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Hydration
Coffee, milk, soup, beer: what each drink counts for
Why a coffee hydrates like water, why a soup counts at 90%, why wine doesn't count, and how a drink from your meal automatically joins your hydration.
4 min read Updated October 9, 2026
The principle
Not all drinks hydrate in the same way, but the differences are often the opposite of what people think. A 2016 study measured how much of each drink the body still retains two hours after drinking it, compared with water: this is the beverage hydration index. Coffee, tea, soda and sports drinks did not differ significantly from water; milk, orange juice and an oral rehydration solution were even retained slightly better. Azetta relies on these results.
The Azetta method
One rule: never more than the volume drunk
Each drink's coefficient is its index, capped at 100%: no drink counts for more than what you drank. Milk (index of about 1.5) therefore counts at 100%, not 150%.
| Drink | Counts at | Suggested serving |
|---|---|---|
| Water, sparkling water | 100% | 250 ml |
| Tea | 100% | 250 ml |
| Coffee | 100% | 150 ml |
| Juice, milk | 100% | 250 ml |
| Soda | 100% | 330 ml |
| Sports drink | 100% | 500 ml |
| Rehydration solution | 100% | 200 ml |
| Light beer (4% or less) | 100% | 330 ml |
| Soup | 90% | 300 ml |
Soup was not in the study: it is counted according to its water content (a broth or clear soup contains 90 to 95%), taking the bottom of the range. Beer only counts if it is 4% or less; strong beer, wine, cider and spirits never count.
From the meal to hydration
When you log a drink in a meal, it joins your hydration — but only if it really is a drink. The database contains an explicit list of about 120 foods recognised as drinks (waters, teas, coffees, juices, milks and plant-based drinks, sodas, sports drinks, soups and broths, light beers). Creams, syrups, lemon juices, sauce stocks, wines and spirits are excluded. Nothing is deduced from the name. One gram logged equals one millilitre drunk.
A scanned product must be liquid and belong to a drinks category; a beer of unknown strength is not counted. For your own foods marked as liquid and counted in your hydration: under 5 kcal per 100 ml, it is water; at least 2.5 g of protein, milk; otherwise, juice.
From hydration to the meal
Conversely, a juice, milk, soda, sports drink, soup or beer added from the Hydration page brings calories: it is also entered in your food diary, in the meal matching the time (before 10:00 breakfast, before 14:00 lunch, before 18:00 snack, then dinner); a drink added for a past day goes into the snack. The two entries are linked: deleting one deletes the other, and editing the meal entry changes the hydration. Water, tea, coffee and rehydration salts stay on the Hydration page.
Why this choice
- The idea that coffee "dehydrates" doesn't stand up to measurements made at usual doses: counting coffee as water is more accurate than penalising it.
- Capping at 100% stops a glass of milk from moving your goal forward more than what you drank.
- Strong alcohol increases urine production: it is more cautious not to count it.
- The explicit list avoids false positives: liquid cream or a syrup are not drinks.
Limits
- The index was measured in young men at rest, drinking a litre in one go: real effects vary with the person and the quantities.
- No drink counts negatively, even a highly caffeinated one.
- Water from solid foods is not counted.
References
- Maughan RJ, Watson P, Cordery PA, et al. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. American Journal of Clinical Nutrition, 2016;103(3):717-723.
- EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). Scientific Opinion on Dietary reference values for water. EFSA Journal, 2010;8(3):1459.