Recommended daily fluid intake, from the EFSA reference values.
The European Food Safety Authority (EFSA) gives an adequate total water intake of roughly 2.0 litres a day for women and 2.5 litres for men. That figure covers all fluid — drinks and the water contained in food. Heat, exertion and illness all raise the requirement.
Yes. The EFSA reference values include all beverages, coffee and tea among them. Caffeine's diuretic effect is weaker than commonly claimed and, in ordinary amounts, does not outweigh the fluid the drink itself provides. Alcoholic drinks are the exception and do not count towards the total.
Yes, though rarely. A very large volume in a short time dilutes the sodium concentration in the blood, a condition called hyponatraemia. It shows up most often in endurance athletes drinking large amounts of plain water during exertion without salts. A healthy person on an ordinary day will not encounter it; the EFSA reference values describe ordinary intake rather than extremes of this kind.
Thirst is a reliable signal for most healthy adults, and urine colour is a simple secondary guide: pale yellow usually indicates enough fluid. The EFSA values are population references rather than an individual target, so counting litres precisely is unnecessary for most people.