If you are lucky and have or know an army or military medic you can receive lactated ringers through intravenous. That treatment is equivalent to 2.5 gallons of water. And it doesn't leave feeling full or bloated. Or if you know a nurse they can provide the same treatment. There are also hydration clinics in my area that charge for this shit.
While I was going through Special Forces SFAS, it was in the middle of June hot as fuck. The cadre issued every soldier oral rehydration salts. I shit you not these oral rehydration salts are the shit. After one training event I didn't hydrate. I had a fucking headache and popped open the oral rehydration salt packet popped it into my canteen drank the whole canteen. And within 5 minutes I was good to go.
Here is the link to the oral rehydration salt packets:
http://www.google.com/shopping/prod...5ijD9JPZAK6P9AUXeMX7MV5qoUNOCcpDHsaAiUt8P8HAQ