Many people freeze bottled water and sports drinks so they have cold beverages on hot summer days. As it melts, you have a cold drink that can last for hours. But experts recommend against this for one reason: The plastic bottles are not designed to be frozen. The chemicals in disposable plastic bottles can leach into the beverage if you subject the plastic to extreme temperatures like freezing or boiling. It’s best to use a chemical-free reusable bottle to freeze your drink, or you can wrap an ice pack around a bottled drink to keep it cold.