Intense exercise causes fluid loss through sweat; drinking before, during, and after activity is essential for recovery.
Not all "extra fluids" have to be plain water. You can reach hydration goals through various sources: Diarrhoea Treatment Guidelines Extra Fluids
Your body requires more hydration when it loses water faster than usual or when it needs support processing waste. Common scenarios include: Intense exercise causes fluid loss through sweat; drinking
Fluid needs increase to approximately 2.3 liters (10 cups) daily during pregnancy and 3.1 liters (13 cups) while breastfeeding to support the body's increased demands. Managing Fluid Intake Extra Fluids