Ever notice in TV shows people seldom eat or go to the bathroom despite it being a major part of being human? Yeah, they leave that out in documentaries too. I guess they figure everyone knows how to piss and shit and so it's non-sequitur. But I get your question here.
I'm sure they go to a porta shitter. In US they keep those things around all training areas. In the past you'd dig a hole with your e-tool, flip it around and use it as a seat, shit, wipe and bury. But training areas quickly turned into cesspools when it rained.
So now they have porta shitters. Usually they're off limits during training exercises (you can't camp on a porta shitter and wait for OPFOR) and they're locted sort of in the middle of the whole shebang as well as randomly throughout the training areas.
While I don't know anything about Hell Week or any schools like that at all, I do know this. Many a time we did not piss or shit for days when the fun an games started. If your working hard an your intake is par or sub par for the latter, you will not shit much. Longest we never pissed was 5 days an that was drinking 2-3 gallons of water each day. (That is very had on the kidneys BTW.) Two boxs of rats is not near enough to shit out working that hard,...besides most of the time,... trying to shit rats was a task in an of it's self,...
I get the constipation, but not pissing for five days? Is that even doable? I could always get a piss in. I've pissed during tactical movements under fire. Pull your dick out, IMT to the next cover, piss while firing, choke it off and combat roll, IMT to the next position and continue. Pissing during forced road marches was no problem at all, keeping up a 4mph pace and pissing while walking. Yeah, BTDT.
Gatorade bottles and ziploc bags are your friend though in concealed positions, say, a sniper's hide. Brits like to take saran wrap.
If there's water involved, I just piss my pants and let the water handle it. Shit's a different story.
And if you've never taken a shit without a Stryker platoon pulling security for you while you did it, all the while laughing at your ass because you're on the thermal display doing it, you ain't lived yet. Something about a fresh poo on thermal and being able to see the heat come off it is, uh, fascinating.
