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One of the most common questions about intermittent fasting isn't "what can I eat", but "what am I allowed to drink". The general rule, backed by sources such as Johns Hopkins Medicine and Mayo Clinic, is simple: any drink with very few or zero calories, that doesn't trigger a significant insulin response, is generally accepted during a fast.
Still and sparkling mineral water
These are the basis of hydration during a fast and don't break it in any way. Sparkling mineral water, without flavourings or sugar, is also allowed and can help with the feeling of fullness.
Coffee (black, with no additions)
Plain black coffee has close to zero calories and is accepted by most fasting protocols. Caffeine can even reduce hunger in the short term. Adding milk, cream or sugar, however, introduces calories and macronutrients that can affect the insulin response, so technically it "breaks" a strict fast.
Tea (green, black, herbal)
Like coffee, unsweetened teas are freely allowed and are a good source of hydration and antioxidants with no meaningful calorie impact.
"Zero calorie" drinks
Artificially sweetened fizzy drinks (zero sugar) contain no calories, but expert opinions are divided on the effect of sweeteners on appetite and the microbiome; Harvard Health recommends moderation rather than unrestricted consumption.
Electrolytes
During longer fasts or restrictive windows such as 18/6 or 20/4, supplementing with sugar-free electrolytes (sodium, potassium, magnesium) can prevent headaches and fatigue without breaking the fast, as long as they don't contain significant calories.
Popular questions
Can I take vitamins in the morning, on an empty stomach?
Water-soluble vitamins are usually well tolerated on an empty stomach; fat-soluble ones (A, D, E, K) are better absorbed with a meal that contains fat, so ideally you take them within your feeding window. Talk to a doctor or pharmacist if you're taking medication that needs to be taken with food.
Does bone broth or clear soup break a fast?
Yes, they contain calories and protein, so they're considered meals, not "neutral" drinks.
Does chewing gum break a fast?
The calorie impact is minimal, but it can slightly stimulate the insulin response in some people; it's a grey area, not a strict no.
Sources and references
Black coffee, without sugar or milk, has practically zero calories and doesn't break your fast; most fasting protocols allow it freely.
A small amount of lemon juice in water has negligible calories and, for most people, doesn't affect the metabolic benefits of fasting.
Sugar-free gum has a minimal calorie impact, but it can slightly stimulate insulin secretion in some people, so it's best consumed in moderation.
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