We recently received this great tip from Lee in California. Lee is a mom of two elementary kids who insist on taking their Vapur to school everyday. To keep the kids' lunches cool throughout the day, she fills the Vapurs half-full with filtered water and freezes overnight. In the morning, she fills them to the top and sticks them in her kids' lunch boxes. This serves to keep lunches cool and water ice-cold (but not frozen). Thanks for the tip Lee!