Besides, dehydration is in no way positive. It's basic knowledge that you should drink f.ex. water after working out to get back to your normal weight.
It will help your body recover more quickly, and develop faster.
I think a sauna suit might be used for self defense though. Your assailant might choke from laughter. =)
OH, and being finnish and all, .. Try a real sauna. It cleanses and relaxes like nothing else.. Especially if you jump into a cold lake afterwards, return to the sauna, repeat, and then pop the cap of a cold beer. And Saunas should be 80-100C.