So much of old D&D is just book keeping. How many iron rations do you have, how many candles? Do we have enough toilet paper? Did we bring 5 iron spikes each? These are things that only really add to the game when the absence is felt, yet require so much micromanagement to keep track of.
This is not only hilarious, but actually relevant to how I run my own campaigns.
No, I do not make my PC's write on their character sheets how much toilet paper they are bringing into the dungeon. We also refrain from discussing or (ugh!) roleplaying the details of how they use it. I think we're generally pretty safe just assuming that they did bring some TP or the fantasy-era equivalent, they are using it just fine without any further explicit comment being necessary, the end.
It generally works the same way for most basic disposable supplies that aren't special in any way, and that can be reasonably assumed to be readily available. At least, it does until it becomes *dun dun dun* A Plot Point.
But what do you do when some smart PC states that they are using the party's entire supply of toilet paper - which the smart guy calculates to be 1.8 cubic feet based on the average toilet paper needs of a party this size that expects to be in the field this long - to do something other than wipe his hairy hobbit bum-bum? Can he set it on fire and instantly create a volume of smoke that defeats an invisibility spell?
Yeah, I'm gonna make a call on toilet paper if something like that comes up. Because it's relevant at that point, so it actually matters how much they had with them, or if they had any at all. Hey, I dunno - maybe they had none because they all used sand or leaves or a cantrip or something. Or the mage's used-up scrolls. Elf mages are totally into recycling and being green and stuff. The point is that when it becomes plot-relevant, you have to make a call, and it has to make logical sense. Even if you do let the hobbit rogue do this once, and you ignore the unhygenic consequences of his action, do you want to let him do it again? Probably not. Sorry, but now you have no more toilet paper in the dungeon. Sucks to be you.
I pretty much handle ammo the same way, especially when it could logically be a retrievable or renewable resource in the environment they're in. But, if the party is pinned down for hours by enemy fire, it's time to start keeping track, because it no longer makes sense to do otherwise. It's a relevant plot point, and therefore it's worth spending bookkeeping time and energy on.
Most common disposables really aren't, though. The game goes smoother if you just let the PC's have their TP. And stuff.