Guess I'm still old-school, I stop to get a drink. A cheap, easy way to keep water cold is
to get a 1 liter soda bottle (Pepsi bottle has a nice large mouth). Fill the bottle with water the night before and freeze it. Before you leave, wrap the bottle with a towel and
use rubber bands or velcro to keep it tight. You can drink from the bottle without unwrapping the towel. You will have cold water all day and when you stop you can use the damp towel to wipe your face. I have had the water stay cold for 8 hours on a hot day! If you don't plan that far in advance you can still fill the bottle with water and ice (my icemaker makes cubes that will fit through the mouth of the bottle) and have cold water for a few hours!