'What are the electrolytes in Gatorade?'

'...the key electrolytes are the minerals sodium, potassium, and chloride. When athletes sweat they lose electrolytes such as sodium, potassium, and chloride that are essential to hydration and muscle function. Unlike water and other beverages that are not scientifically formulated, Gatorade is lab-tested to ensure it helps replenish the electrolytes lost in sweat and stimulates thirst so that athletes will ingest an adequate amount of fluid and electrolytes to stay better well-hydrated compared to when using beverages without electrolytes, particularly sodium.'

http://www.gatorade.com/frequently_asked_questions/default.aspx