Isotonic Drink  Make this mixture for rehydration, for example after diarrhea or endurance sports. The baking soda delays the lactic acid, which is the body’s waste product of tired muscles from physical effort. In a large cup mix 1 tablespoon of castor sugar (dissolves better), 1/2 teaspoon of salt and 3/4 teaspoon of baking soda. Add to the mixture 1/4 glass of water, mix and top up with lemonade. Experiment the dosage according to your personal preference.