Originally Posted by Carbonfiberboy

For long hot rides, I fill my 70 oz. Camelbak with ice, then add water. Works great. Been using it for decades. The way to keep cool on the bike is to sweat. The way to sweat is to drink. When you stop sweating, you are in deep trouble, right now. Taking plenty of water is what you do. A big advantage of a Camelbak on the bike is that you're more likely to drink because it's so convenient and safe with both hands on the bars and no bottle to distract.