I've heard you could pour booze into your butt and somehow get drunk.
The thing is, the colon is amazing at absorbing anything you put into it. It's a legit method of drug administration. Some drugs just get broken down to useless garbage during digestion if you swallow them, so the colon is often a viable backup route for those drugs. At least, that's what Wikipedia tells me.
But no, I'm not gonna give myself an Everclear Enema to get drunk. Not that I'd touch the stuff in the first place, either.
Which raises an interesting question: why? What evolutionary advantage does a super absorbent colon give us? Water retention?
Well, technically yes... But also everything else as well. It's part of your digestive tract. The stomach doesn't absorb anything, it just melts everything coming in until it becomes a nice mushy slurp, which then gets passed on into the intestines where it's further processed by bacteria (gut flora) and all the necessary nutrients and moisture get absorbed from it.
As the mush passes through the various stages of intestine, its makeup gets changed by the bacterial presence breaking it down into different things, so we need to be able to absorb different things at different times as it gets worked on.
Getting the final drops out of the nutrient mush as it's on its way through is useful both in terms of water/nutrition intake, and also for making sure that the final waste has an appropriate amount of moisture in it and isn't just runny diarrhea, which would be much more of a health risk due to it getting stuck on everything and spreading around.
There's probably also some sort of interaction between plant vs. animal matter getting processed and how quickly it's supposed to get passed out of the system, as humans have generally much longer intestinal tracts than obligate carnivores, but I really do not know enough about any of this to be able to provide more than pure speculation.