When I'm doing a long ride on a hot humid day day I use Tim Horton's stainless steel thermos bottles mounted onto the main triangle of the frame. They keep the water refreshingly COLD for many, many hours. On this bicycle I have a regular water bottle mounted on the handlebar and I decant about one cup of water from the stainless steel thermos into that regular water bottle and sip from the water bottle as I ride.
Cheers