For races lasting less than 1 hour, water alone is adequate. For longer races, there are many commercially available sports drinks. The most important features are taste, carbohydrate and sodium content. Taste is important, because if you don't like it you won't drink it. Don't try a new sports drink on race day.
Higher levels are better for salt replacement, but tend to be less palatable.
Salt important Sweat contains between 2.25 to 3.4 grams of sodium chloride per liter. A sweat rate of 1 liter per hour would thus cause a salt loss of 27- 40 grams for a 12 hour race. One teaspoon of salt weighs approx. It is also advisable to increase salt intake for several days before a long race. The higher the intensity of exercise the greater heat production by the muscles.