The BHI measures how well a drink hydrates you compared with plain still water (BHI = 1.00). Higher scores mean more fluid was retained two hours after one litre. Values marked ≈ are read from the study chart; ORS, full-fat milk, skim milk and orange juice were significantly higher than water.
| Beverage | BHI | Status |
|---|---|---|
| Skim (fat-free) milk | 1.58 | Higher retention than water |
| Oral rehydration solution (ORS) | 1.54 | Higher retention than water |
| Whole milk (full-fat) | 1.50 | Higher retention than water |
| Orange juice | ≈1.4 | Higher retention than water |
| Protein shake (milk-based) | ~1.2–1.5 | Similar to water |
| Cola (regular) | ≈1.2 | Similar to water |
| Latte / cappuccino | ~1.1–1.4 | Similar to water |
| Bone broth / soup | ~1.1–1.4 | Similar to water |
| Soy milk | ~1.0–1.3 | Similar to water |
| Oat milk | ~1.0–1.2 | Similar to water |
| Fruit smoothie | ~1.0–1.2 | Similar to water |
| Cola (diet) | ≈1.1 | Similar to water |
| Iced tea | ≈1.1 | Similar to water |
| Coconut water | ~1.0–1.1 | Similar to water |
| Apple juice | ~1.0–1.1 | Similar to water |
| Hot tea (black) | ≈1.0 | Similar to water |
| Sports drink (Powerade-type) | ≈1.0 | Similar to water |
| Still water | 1.00 | Similar to water |
| Green tea | ~1.0 | Similar to water |
| Herbal tea (caffeine-free) | ~1.0 | Similar to water |
| Espresso (single, 30 ml) | ~1.0 | Similar to water |
| Kombucha | ~0.9–1.0 | Similar to water |
| Lager beer (~4% ABV) | ≈1.0 | Similar to water |
| Sparkling / mineral water | ≈1.0 | Similar to water |
| Energy drink | ~0.9–1.0 | Comparable, with trade-offs |
| Coffee (black, instant) | ≈0.9 | Similar to water |
| Wine (~12% ABV) | ~0.7–0.9 | Likely reduced retention |
| Cocktail (spirit + mixer) | ~0.6–0.9 | Likely reduced retention |
| Spirits (~40% ABV, neat) | insufficient evidence | Likely reduced retention |
Coffee (~212 mg caffeine per litre) was not significantly different from water in the trial. See does coffee dehydrate you? for the full evidence.
Short answer: yes, all three count toward your daily fluid intake.
Black tea and iced tea scored about the same as water in the BHI trial (neither differed significantly from water; the tea contained roughly 179 mg caffeine per litre). In a separate trial of 21 healthy men at rest (Ruxton & Hart, British Journal of Nutrition, 2011), 4 × 240 ml or 6 × 240 ml of black tea, served across the day, produced no significant difference from equal volumes of water in the measured blood and urine markers. The tea included a small amount of milk. This supports similar hydration for the black tea and amounts studied, not a claim about all teas or people; herbal teas and very strong tea were not tested.
Yes, for plain sparkling water. In the BHI trial, carbonated water was not significantly different from still water over two hours. Flavoured or sweetened sparkling drinks add other ingredients.
In the BHI trial, full-fat milk (1.50) and skim milk (1.58) kept more fluid in the body at two hours than water. A post-exercise study (Shirreffs et al., British Journal of Nutrition, 2007) also found milk was retained better than water or a sports drink. This does not mean milk should replace water: the BHI was one study in 72 healthy, fasted men drinking one litre at rest, measured over two hours. See the water intake calculator and sources.