Two cups of water weigh one pound. Dehydration can lead to a loss in strength, concentration, endurance, coordination, and aerobic capacity. This amount increases for excessive sweating in hot weather. Individual differences also exist. A person who sweats more than average will require a higher fluid intake.
Plain water is best.
However, milk, juice, or sport drinks can be used. Sport drinks may benefit endurance athletes by acting as a carbohydrate source during long training sessions or events. An athlete should experiment with sport drinks before competition to avoid gastric upset which could result in poor performance. Soda and juices contain higher amounts of sugar than sport drinks and should be avoided during exercise. They can cause cramping, diarrhea, and nausea.