I'm freezing a combination of Endurox/ice cubes in it, filled to an inch from the top, with the top off. Then it rides an hour in a cooler of ice, then I ride four-six hours in 80-95 heat. So I'm probably not giving it a fair chance. But a couple times, now, after only two-three hours, the Endurox has tasted like warm, sour milk. Yuk.

Nanci