Sports drinks are beverages that are specially formulated to help people rehydrate during or after exercise. They are usually rich in carbohydrates – the most efficient source of energy. As well as carbs, which are important in maintaining exercise and sport performance, sports drinks usually contain sweeteners and preservatives. Sports drinks also contain electrolytes (minerals such as chloride, calcium, magnesium, sodium and potassium), which, along with body fluid, diminish as you exercise and sweat. Replacing the electrolytes lost during training promotes proper rehydration, which is important in delaying the onset of fatigue during exercise.