US experts say the commonly cited 3.7 L (men) and 2.7 L (women) figures count all fluids, and about 20% comes from food. Drinks-based fluid need is nearer 3 L for men and 2 L for women, roughly 6-8 and 4-6 average US glasses. Coffee, tea and sparkling water count toward intake; alcohol works against it. Check urine colour: pale yellow is the target. This is general background, not a business change, so no action is needed beyond staff water access in hot workplaces.