New York's attorney general is investigating whether the multibillion-dollar energy-drink industry is deceiving consumers with misstatements about the ingredients and health value of its products.

Eric T. Schneiderman issued subpoenas in July to PepsiCo Inc., maker of AMP, Monster Beverage Corp., and Living Essentials LLC, maker of 5-hour Energy drink, according to a person familiar with the matter. The subpoenas asked for information on the companies' marketing and advertising practices.

The...