How much water (in litres) should a male teenager drink each day?

Daily fluid intake: General recommendation is 2 litres (68 fl oz or 2+ quarts) of fluid intake per day as the body eliminates this quantity of fluid every day through the skin, lungs, bladder and intestines. Children may not drink enough because their feeling of thirst is not developed enough. They also have a higher fluid requirement if it's hot or they're very active. High altitudes & cold climates also req more.

Don't complicate it: The fluid value a kid needs to consume is what it takes to make pee every 6 hours. They get fluid value from foods (apple sauce is 95% water,vegies 60%) as well as fluids themselves.As long as the kid has normal kidney function, you do not need to set random targets.