God has given me two great ideas for coping with heat, e.g. when you’re in a non-air-conditioned vehicle on a hot day.
Idea 1: a spray bottle. Big spray bottles for your car; or a small one to carry in your bag.
Idea 2: A bottle of cold water is nice, but in blazing heat it doesn’t stay cold for very long. Try this trick for cold water that lasts a few hours instead of a few minutes:
The night before you need to spend a few hours in the heat, fill a plastic water bottle NOT all the way, and put it in the freezer in a tilted orientation:
The next morning when it’s frozen, add water on top of the ice. You can start drinking cold water in a couple minutes, and the gradually-melting ice will give you sips of cold water for the next few hours.