My first combat hop in the NAG, I had a 50oz camel back on my flight gear, as well as a two liter bottle of water with me. By the time I ever made it to the catapult (45 minutes from stepping on the flight deck), I had completely downed the two liter bottle of water, and I had sweat through my flight suit, g-suit, and my harness. My the ties under the back of my helmet from my do-rag/skull cap were like a faucet pouring all the sweat down my back.
It was even more awesome coming back to the ship 8 hours later, and going to my 100 degree (not lying) stateroom.
I sweat through my boots on most days. It's not uncommon to have mics stop working from sweat in them. The worst is my zeta liner, which, after a couple of hours of flying in the gulf, is like a giant sweat filled sponge. Any movement of my head makes sweat pour down my face. Nasty.