An isotonic drink is a sports drink, rich in carbohydrates, whose concentration of compounds is close to that of blood. It promotes gastric emptying, that is, the arrival of nutrients to the blood and their absorption. On average, to maintain its isotonic properties, a sports drink contains between 50 and 80 grams of carbohydrates per liter of water. Below this level, we speak of a hypotonic drink, that is, the concentration of nutrients is lower than that of blood, thus promoting hydration. Above this level, we speak of a hypertonic drink. The drink concentrates a greater proportion of nutrients than that of blood and forces the body to dilute the product through the water it contains, often leading to digestive problems (this is also the case when consuming a gel without water).