Over the past few decades, numerous studies have been carried out to establish the optimal composition of drinks that are designed to rehydrate the body rapidly. These studies have led to the insight that drinks should contain carbohydrate (CHO) and sodium to stimulate fluid absorption and fluid retention. However, the CHO content as well as the osmolality of the drink should be relatively low. According to these findings, the composition criteria for rehydration drinks have quite a narrow range. Drinks that are designed to supply energy or substances that stimulate energy metabolism differ considerably in their composition. This review highlights the most relevant aspects.