Abstract: An evaporative cooling device for beverage containers that uses hydrated polymer crystals within a sleeve-like cover to lower the temperature of a liquid contained within a conventional beverage container for an extended period of time through evaporative cooling. Made from flexible material, the device will have a flexible body conform to the shape of a wide variety of beverage containers. The evaporative cooling device is held to the beverage container by the increase in volume of the hydrated polymer crystals.