Lycopene, however, is fat-soluble, meaning that it needs certain fats in the blood for better absorption by the body. Watermelon consists of 92% water and 8% sugar. Watermelon can help improve sleep. By eating a few slices of this fruit after dinner can extend the deep stages of sleep by 27%. The reason is watermelon's polysaccharide carbohydrates rev the body's output of serotonin.