Remember, they will be down there for four months and we want them to be sane when they get out, and not all emo and stuff.
Nothing in Nothing out comes to mind when talking about waste products. There is no need for them to eat a lot or drink more than they will excrete through their skin via sweat or by breathing.
How big is the hole? Could they send down something like an air hose that could be used to sucking urine out of the area? Is the hole big enough to retrieve ziplock bags full of poo?
Just thinking, they have been down there for 20 days and it is probably as bad as it will get smell wise as their bodies are probably used to very low calorie digestion and not excreting much.
They will have to be brought back onto normal food gently when they get out or there will be big problems as their systems will not be able to deal with anything protein dense.
Drop down some old tetris game boys. I know there were times when it felt like I was playing that thing for 4 months straight as a kid.