With regard to exercise, fluids are a coolant. They are also the medium through which nutrients are transported to our muscles and organs. Inadequate hydration is a major cause of poor performance, fatigue, and even illness during a game or practice. When sweat loss exceeds three percent of body weight, it will usually impair performance. This is especially important on days when both temperature and humidity are high.
Water is always an excellent replacement drink.
Some commercial drinks are also good. The high sugar content slows the fluid absorption from the stomach. The caffeine is a diuretic, which causes you to urinate when you are trying to retain fluid. The carbonation makes you feel full, so you may not drink enough fluid to satisfy your body's need for fluid. Drinks with some carbohydrate is good.