What Breaks a Fast? A Practical Guide to Food, Drinks, and Common Add-Ins
“What breaks a fast?” sounds like a simple yes-or-no question, but the answer depends on what you mean by fasting.
For a strict zero-calorie fast, consuming calories means you are no longer following a zero-calorie fast. For everyday intermittent fasting (such as an 16:8 schedule), people commonly use water and other low- or zero-calorie drinks during the fasting window.
That distinction matters because the internet often treats every fasting question as if there is one universal rule.
There isn't.
This guide uses a practical definition for intermittent fasting: if something provides meaningful calories or is being consumed as food, it belongs in the eating window rather than the fasting window. For beverages with very little energy, the answer can be more nuanced. For a broad introduction, see our intermittent fasting guide for beginners and our guide on how to choose a fasting window.
The Simple Rule
If your goal is to keep a strict zero-calorie fasting window, the simplest rule is:
No food and no calorie-containing drinks during the fasting window.
Water is the clearest choice. Plain black coffee and unsweetened tea are commonly used during intermittent fasting because they contain very little energy, but they are not the same thing as water in every research or fasting context.
Once you add sugar, honey, milk, cream, juice, or another calorie-containing ingredient, you have added energy to the fasting period.
The National Institute on Aging describes time-restricted eating as eating within a limited number of hours each day, with nothing consumed during the other hours.
What Usually Does and Does Not Break a Fast?
Here's a practical starting point:
| Item | Practical fasting-window answer |
|---|---|
| Plain water | Does not add calories |
| Sparkling water, unsweetened | Does not add calories |
| Black coffee | Very little energy; commonly used during IF |
| Plain unsweetened tea | Very little energy; commonly used during IF |
| Coffee with sugar | Breaks a zero-calorie fast |
| Coffee with milk or cream | Adds calories; breaks a strict zero-calorie fast |
| Sweetened tea | Breaks a zero-calorie fast |
| Juice | Breaks a zero-calorie fast |
| Regular soft drinks | Breaks a zero-calorie fast |
| Protein shakes | Breaks a fast |
| Bone broth | Contains energy/protein; not a zero-calorie fast |
| Calorie-containing electrolytes | Break a zero-calorie fast |
| Zero-calorie electrolytes | No calories, but check the label and purpose of the fast |
| Sugar-free gum | Depends on formulation and your definition of fasting |
| Non-nutritive sweeteners | Little/no energy in many products, but effects beyond calories are not identical |
The table is a practical guide, not a medical or laboratory definition of every type of fasting. For full beverage details, see our comprehensive guide on what you can drink while fasting.
Does Water Break a Fast?
Plain water does not provide calories, so it is the simplest beverage to use during a fasting window.
Still or sparkling water can both work as long as the product does not contain sugar or another calorie-containing ingredient.
Flavored waters need a label check. Some are effectively calorie-free, while others contain sugar or other ingredients that add energy.
For ordinary intermittent fasting, hydration is important. If you're using a fasting schedule, water is generally the easiest choice when you want to avoid questions about whether a drink contains calories.
Does Black Coffee Break a Fast?
Plain black coffee is one of the most common questions.
Plain black coffee contains very little energy, and it is commonly included in intermittent-fasting routines. Johns Hopkins Medicine describes intermittent fasting as restricting eating to specific time windows and discusses daily schedules such as 16:8.
However, black coffee is not the same as a strict water-only fast.
If you are following a strict zero-calorie protocol, water is the clearest option. If you are following a typical time-restricted eating routine, plain black coffee is commonly used during the fasting period.
The important difference is what you add to it.
What about coffee with sugar?
Sugar adds calories.
So:
Black coffee → generally compatible with a typical intermittent-fasting window
Coffee + sugar → no longer zero-calorie
What about coffee with milk or cream?
Milk and cream add calories and nutrients.
If you're trying to maintain a strict zero-calorie fasting window, adding them means you have consumed calories during the fast.
You can instead keep milk or cream inside your eating window.
Does Tea Break a Fast?
Plain, unsweetened tea is similar to black coffee in practical intermittent-fasting terms: it contains very little energy and is commonly used during fasting windows.
That includes many plain teas such as black tea and green tea.
The main issue is what gets added to the drink.
- Plain unsweetened tea: very little energy.
- Tea + sugar/honey: adds calories.
- Tea + milk: adds calories.
- Sweetened bottled tea: check the nutrition label; many products contain sugar.
Mayo Clinic describes intermittent fasting as periods with very few or no calories.
Does Milk Break a Fast?
Yes, milk contains calories, carbohydrate, protein, and other nutrients, so it breaks a strict zero-calorie fast.
This applies whether the milk is added to coffee, tea, or consumed by itself.
The same practical rule applies to many milk alternatives. Unsweetened plant milks can vary considerably by product, so check the nutrition label rather than assuming that “plant-based” means calorie-free.
If you want milk in your coffee or tea, the simplest approach is to have that drink during your eating window.
Does Sugar Break a Fast?
Yes.
Sugar provides calories, so adding sugar to coffee, tea, water, or another drink ends a strict zero-calorie fast.
This includes:
- table sugar
- brown sugar
- honey
- syrups
- sweetened drink mixes
Calling a sweetener “natural” does not make it calorie-free.
If your goal is a strict no-calorie fasting window, keep caloric sweeteners inside your eating window.
Do Artificial Sweeteners Break a Fast?
This question is more complicated than a simple yes or no.
Many non-nutritive sweeteners provide little or no energy in the amounts normally used. That means they do not fit the same category as sugar, honey, or syrup from a calorie perspective.
However, different sweeteners and products are not identical, and questions about appetite, metabolic responses, and individual effects are more complicated than simply counting calories.
For a straightforward intermittent-fasting routine, the simplest approach is to avoid relying heavily on sweetened drinks during the fasting window. If you use a zero- or near-zero-calorie product, check the label and ingredients.
Most importantly, don't turn a small amount of a non-caloric sweetener into a claim that it either “destroys all fasting benefits” or is guaranteed to have no effect. The evidence does not support that kind of universal statement.
Does Gum Break a Fast?
It depends on the gum and on how strictly you define the fast.
Regular chewing gum often contains sugar and therefore adds calories.
Sugar-free gum generally contains little or no sugar, but it can still contain small amounts of energy from sweeteners or sugar alcohols.
So there are two practical approaches:
- Strict zero-calorie fast: skip gum if you want the simplest possible rule.
- Typical intermittent-fasting routine: a small amount of sugar-free gum may be treated differently because its energy contribution can be very small, but it is not necessary to use gum during the fasting window.
If you are unsure, check the nutrition label rather than assuming that “sugar-free” means literally zero calories.
Do Electrolytes Break a Fast?
It depends on the product.
An electrolyte drink can contain sodium, potassium, magnesium, and other ingredients. Some products also contain sugar, carbohydrates, or other calorie-containing ingredients.
Therefore:
Calorie-containing electrolyte drink → breaks a strict zero-calorie fast.
Zero-calorie electrolyte product → does not add calories, but the product's ingredients and your reason for fasting still matter.
Read the nutrition label and ingredient list.
There is also an important safety distinction: electrolyte needs are not identical for everyone, and longer or medically supervised fasts can raise questions that a simple intermittent-fasting guide cannot answer.
For an ordinary daily fasting schedule, plain water is usually the simplest default.
Do Vitamins and Supplements Break a Fast?
There is no single rule for every supplement because formulations differ.
A capsule may contain very little energy, while a gummy supplement can contain sugar or other calorie-containing ingredients. Protein powders, collagen products, amino-acid products, and meal-replacement supplements are clearly not equivalent to a calorie-free drink.
If a supplement contains meaningful calories, protein, carbohydrate, or fat, it does not fit a strict zero-calorie fasting window.
Also consider the instructions for the supplement itself. Some products are intended to be taken with food, and changing when you take medication or supplements can have practical consequences.
Don't change prescribed medication timing just to maintain a fasting window without discussing it with your healthcare professional.
Does Lemon Water Break a Fast?
Plain water with a small amount of lemon can be a gray area depending on how strict your definition is.
A few drops of lemon juice contribute some energy, but a large glass of lemon juice is clearly a calorie-containing drink.
So the practical distinction is:
- Plain water: no calories.
- Water with a small amount of lemon: contains a small amount of energy.
- Lemonade or sweetened lemon water: contains substantially more calories if sugar is added.
If your priority is a strict zero-calorie fast, plain water removes the ambiguity.
Does Bone Broth Break a Fast?
Yes, for a strict zero-calorie fasting window.
Bone broth is food in liquid form and can contain calories, protein, and other nutrients. It is therefore different from plain water or a calorie-free beverage.
Some fasting approaches use broth during modified fasts, but that is not the same as a zero-calorie fast.
So don't use the phrase “fasting-friendly” as if it were a universal scientific category. Ask what kind of fasting protocol you are actually following.
What About Protein Powder, BCAAs, or Collagen?
These products contain nutrients that are intended to be consumed, not simply used as hydration.
Protein powder provides protein and calories. Collagen products can provide protein. BCAA products provide amino acids.
They therefore do not belong in a strict zero-calorie fasting window.
If you use these products around exercise, place them within your eating window if maintaining the fasting period is important to you.
What About Diet Soda?
Diet soda can be complicated because many products contain little or no calories but use non-nutritive sweeteners.
From a calorie-only perspective, a zero-calorie drink is different from a sugar-sweetened drink.
But “zero calories” does not mean that every physiological question about every sweetener has been settled. Product formulations also vary.
If your goal is a simple, uncomplicated fasting routine, water, plain tea, or black coffee are easier choices.
What If I Accidentally Eat or Drink Something?
Don't assume that one small mistake means you have ruined your entire routine.
If you consume something that contains calories during your fasting window, you can simply treat that point as the end of that particular fast and continue with your normal schedule.
For example, if you intended to fast until noon but added sugar to your coffee at 10 AM, there is no need to turn the rest of the day into an all-or-nothing exercise.
The purpose of a recurring fasting schedule is to create a routine you can follow consistently, not to create a test where one small deviation invalidates everything.
Strict Fast vs Practical Intermittent Fasting
A lot of confusion comes from using the word “fast” without defining the context.
Strict zero-calorie fast
The rule is straightforward: No calories.
Water is the simplest option. Caloric drinks, food, protein, sugar, milk, cream, and broth do not fit this definition.
Typical intermittent fasting
Time-restricted eating focuses on keeping food intake within a defined eating window. During the fasting period, people commonly choose water, plain tea, or black coffee.
This is a practical routine rather than a laboratory protocol.
Medical or laboratory fasting
Medical tests and procedures can have their own instructions. If a healthcare professional tells you to fast before a test, procedure, or medication, follow those instructions rather than using an internet fasting guide.
The rules for a medical fast can be different from the rules for a lifestyle intermittent-fasting schedule.
A Simple Way to Decide
When you are unsure whether something breaks your fast, ask three questions:
- 1Does it contain calories?
- 2Is it food or a nutrient-containing supplement?
- 3What type of fast am I actually trying to follow?
Sugar, honey, milk, cream, bone broth, juices, protein shakes.
Plain black coffee, unsweetened green/black teas, sparkling water.
Still water, mineral water with zero calories and no additives.
If the answer to the first question is yes, it does not fit a strict zero-calorie fast.
If the product is marketed as “fasting-friendly,” don't rely on the marketing label. Check its nutrition facts and ingredients.
Frequently Asked Questions
Does coffee break a fast?
Plain black coffee contains very little energy and is commonly used during intermittent fasting. Coffee with sugar, milk, cream, or other calorie-containing additions does not fit a strict zero-calorie fast.
Does tea break a fast?
Plain, unsweetened tea contains very little energy and is commonly used during intermittent fasting. Sugar, honey, milk, and other caloric additions change the answer.
Does milk break a fast?
Yes. Milk contains calories and nutrients, so it breaks a strict zero-calorie fast.
Does sugar break a fast?
Yes. Sugar provides calories and breaks a strict zero-calorie fast.
Does sugar-free gum break a fast?
It depends on the formulation and how strictly you define the fast. If you want a simple zero-calorie rule, skip gum during the fasting window.
Do electrolytes break a fast?
It depends on the product. Electrolytes containing sugar or other calories break a strict zero-calorie fast. Zero-calorie products do not add calories, but you should still check the label and consider the reason for your fast.
Can I drink water while fasting?
Yes. Plain water contains no calories and is the simplest drink during a fasting window.
Can I use artificial sweeteners while fasting?
Many non-nutritive sweeteners provide little or no energy, but different products and sweeteners are not identical. If you want the simplest fasting routine, water, plain tea, or black coffee avoid most of this uncertainty.
What breaks a fast the fastest?
There is no useful need to rank foods or drinks by how quickly they “break” a fast. For a strict zero-calorie definition, consuming calories means the zero-calorie fast has ended.
Safety Note
This article is general educational information, not individualized medical advice.
Fasting is not appropriate for everyone. Johns Hopkins Medicine notes that people with certain conditions, including people using insulin for type 1 diabetes and people with a history of eating disorders, require particular caution.
Mayo Clinic also notes that fasting may not be appropriate for everyone and recommends discussing fasting with a healthcare professional in relevant circumstances.
If you are pregnant or breastfeeding, under 18, have a medical condition, take medication affected by food timing, or have a history of an eating disorder, seek individualized professional guidance before changing your eating pattern.
Key Takeaways
- A strict zero-calorie fast means avoiding calorie-containing food and drinks.
- Plain water is the simplest fasting beverage.
- Black coffee and unsweetened tea are commonly used during intermittent fasting because they contain very little energy.
- Sugar, milk, cream, juice, protein drinks, and other calorie-containing additions break a strict zero-calorie fast.
- Sweeteners, gum, lemon water, and electrolytes require more attention to the specific product and the definition of fasting being used.
- Medical or laboratory fasting instructions should take priority over general intermittent-fasting advice.
- If you want to calculate exactly when your fasting and eating windows start and end, use the FastTrack Fasting Calculator.
Ready to check your schedule? Use the FastTrack Fasting Calculator to calculate your fasting and eating windows.