A study from Texas Christian University shows that sports drinks help you exercise longer than drinking just water, but they will not help you as much as eating salted food and drinking water.

Most sport drinks contain water, sugar and salt to help you exercise longer. You need lots of water for prolonged exercise, and salt is necessary to make you thirsty so you will drink more. A drink containing lots of salt tastes awful and you would not drink it. The manufacturers of sports drinks know this, so they only add a little salt to their products. You will take in more salt if you eat salted foods and you will drink the most of the beverage that tastes best to you. Dilute fruit juice and salted potato chips, soda and salted peanuts, or any other combination of salted foods and beverages you like, will prolong endurance better than any sports drink.