I have leather pouches mounted on both sides of my bike in front of the saddlebags, so I can always have a bottle of water at the ready. However, since they are BLACK leather, the water doesn't stay cool very long! So, I save my water bottles, preferably the ones with the sippy-top (sport bottle), and fill them half full and freeze them. Then, before I ride, I top them off from the tap, and the water stays cool from the ice, and as the day goes on, the ice melts but I have a constant supply of cold water.
I think the addition of salt might be a good thing, too. I am going to try that, since I have had moments in the past few weeks where I suddenly feel lightheaded and weak. One day I even dropped the bike...one of those abrupt stops when I cager did something unexpected and stupid, and my front wheel was already turned and I over-reacted grabbing the brake. What surprised me the most was how my leg just buckled under the weight of the bike...I can usually keep it from falling over when it gets out of shape like that, but I wasn't having a good day that day!