Smartwater is water that contains electrolytes. The electrolytes in Smartwater are added for taste and may not be enough to replace lost electrolytes during the hot summer months. An 8 oz. serving of Smartwater contains 0 calories, 0 carbohydrates, 2.5 mg of potassium, 2.5 mg of calcium and 3.75 mg of magnesium. (Vapor Distilled Water, Calcium Chloride, Magnesium Chloride and Potassium Bicarbonate.)
The folks at Ideal Protein are recommending Powerade ZERO. It has no carbs or calories and comes in 12 flavors.