Regulating Body Fluids In The Body

First, fluids are absorbed through the gut and into the bloodstream faster when their permeability closely matches that of body fluids such as blood.
Sports drinks contain dissolved minerals (sodium, etc.) and carbohydrates, whereas water doesn’t, so water doesn’t reach the bloodstream as quickly.
Sodium and other nutrients also play important roles in regulating fluid balance in the body. In other words, they help determine how much fluid enters into muscle fibers and other cells, how remains in the blood, and so forth. Again, because sports drinks contain these nutrients, they do a better job of allowing the body to maintain optimal fluid balance,
which is an important aspect of hydration.
While exercising for short periods of time, it is not necessary to replace electrolytes; however, athletes and marathon participants exercising for period of an hour or more can benefit from electrolyte replacement in particular. Carbohydrates offer the body energy. When the body burns calories, it needs carbohydrates to replace energy lost. The longer the workout, the more carbohydrates are needed.
Sports drinks VS water comes down to the length and intensity of an athlete or exerciser’s workout; water is never a poor choice, but there are benefits to supplementing a workout with some varieties of sports drinks as well. More important than selecting between the two is maintaining the proper hydration before, during and after exercise.
A third advantage of sports drinks over water with respect to hydration is that the sodium content of sports drinks stimulates thirst, so athletes usually drink more when they have a sport drink than when they have plain water.