Slightly off topic, ..when we went with 6 kids. first day everyone got a bottle, kids drank some and then bottle flipping, spilling, water got warm....... The next couple of days, I bought a stack of small paper cups. Younger kids got cups, old kids got the 2/3 empty bottle. Everyone got a cold drink of water using two bottles. Kids still thirsty? Break out another bottle and give everyone a bit. No more keeping track of who's bottle is this.