Mug full of warm coffee (preferred cream)
Urge to take a crap
Okay, I've just done this a few hours ago for fun for the second time. I'll warn you that if you do try this, get a huge glass of water and maybe be around with someone just in case something does happen. Yes, it'll be harder to breathe and it'll take like 15 minutes before you'll feel normal again.
So, you get a mug of nice creamy coffee and have the urge to take a crap.
Step 1: Go to the bathroom and sit there with coffee.
Step 2: Hold the the coffee until the last minute you take the crap.
Step 3: Chug the coffee, wait 10 seconds, and then take the crap.
Step 4: Feel prepared to be dehydrated as hell in 15-30 seconds.
Now the reason why I posted this here is because I want to know why you feel dehydrated after drinking coffee and taking a crap. This isn't a joke, try it yourself. Maybe someone here that knows about the human body can explain?