Another thing I've seen is Camelbacks, with water, orange juice, vodka, you know whatever...
I put a motorcycle helmet interior into my original helmet, so I had ear/cheek cushions to prevent wobbling and nice padding everywhere for comfort, I also used 3 computer fans (2 in 1 out at mouth for circulation an pushing out hot breath) run off a 12 volt lantern battery in my backpack, and 4 leds.