Glaceau Smart Water is mostly derived from tap water, but purified of all minerals and enhanced with potassium, electrolytes and magnesium chloride for taste. The website argues that Smart Water doesn't offer any scientific benefits over other purified water, since it uses standard purification methods.
According to a taste test, most people could not tell the difference between the taste of Smart Water and the taste of tap water, says DietSpotlight. The water does contain hydrating electrolytes, but in a smaller amount than sport drinks such as Gatorade. While the water is hydrating, it is not recommended as a replacement for electrolyte-containing sports drinks.