What would be the proper verb, or is there even one? When you give someone food to eat, you're feeding them. But when you give them liquid to drink, what are you doing then? Still feeding them? Despite the fact they're not eating but drinking?

I talk about "watering" someone. I use it more as a joke, since you really only water plants and horses, though.

There are longer ways to say it: I'm quenching someone's thirst, I'm providing them with refreshment, etc. But I think you found a hole in the English language. Nice one.

Food - Any nutritious substance that people or animals eat or drink, or that plants absorb, in order to maintain life and growth
Feeding - Giving someone food

Therefore, feeding could be giving someone a drink

Yeah, this is the kind of stuff that occupies my mind a lot of the time. Like, why do remotes have an "Eject" button? Exactly what kind of convenience is that offering? Regardless of whether you eject the disc/tape remotely or manually, you STILL have to get up and change what's inside. There's really no reason for that eject button to exist.

Hydrating..? dunno

Enema?

ive worked in numerous hospitals or health facilities, and at a few of them i come across the term watering, as previously mentioned, when it comes to providing a client/patient with a drink, or making sure they are adequately hydrated etc.

it seems a bit demeaning, but there it is. i guess it is because of a hole in the english language that this word is used lol.