I can say "I feed someone". Am I forced to say "I give someone a drink", or is there a single word for this (as in "I [verb] someone")? Unfortunately my thesaurus can't really help me.
I don't think there is a single transitive verb for "give drink to [someone]".
If that someone is an animal, you could use water, as in to feed and water a horse:
I didn't go anywhere the next day except up to Grandpa's to feed and water the horse and mule and Granny's chickens.
However, it's unlikely you would use this for a person; the phrase fed and watered refers almost exclusively to livestock, and watered, alone, more to plants, as in I watered the geranium today. It can be used humorously, for example, if you say to a host upon your arrival, to mean that you've already eaten, "No worries; we've already been fed and watered."
If that someone is a baby, you can also suckle them—but this word has even narrower application.
You might try a synonym of sorts for "give," and let the context fill in that a drink was given: (as waitstaff) I served her, I delivered his order; (at the table) I poured her some, I filled his glass.
Approaching this question etymologically:
"Feed" is not related to "eat" because the former originally means to "foster", "nourish" or "protect". See Etymonline's entry for feed.
Similarly "nourish" has cognates in French "nourrir" (to feed) and "nourriture" (food), but notice how "nourrice" (nanny) refers to the woman who looks after (and used to give milk to) a child. In fact, it is said one "feeds milk to a baby" or "breast-feed", hence it is applicable to liquids too.
It is possible the word "food" narrowed down to non-liquid edibles in time, but in the field of nutrition, "food" refers to drinks as well. See: http://en.wikipedia.org/wiki/Food
Funnily enough, the PIE root of "feed" is *PA- and is also found in Sanskrit as two synonyms √pā which can either mean "to protect" (3rd person indicative present pāti) or "to drink" (3rd person indicative present pibati). See: http://www.sanskrit-lexicon.uni-koeln.de/cgi-bin/monier/serveimg.pl?file=/scans/MWScan/MWScanjpg/mw0612-pazubandhaka.jpg
Etymologically speaking again, "to drench" relates more to "to drink" see: http://www.etymonline.com/index.php?term=drench
So in fact it is not so much "to drink" as it is "to eat" that is in need of a causative. :)
I'm going to say there isn't a single transitive verb for "to give someone drink" as there is for "to give someone food". The word "water" can be used as a transitive verb in the context of caring for animals, as in "feeding and watering the horses". The same term "fed and watered" is sometimes used in the context of people, but the verb "watered" for supplying drink virtually always follows being fed; if you were to hear of someone "watering" someone else the immediate mental picture is of spraying them with a hose or sprinkler like a lawn or garden.
I think "hydrate" is a bit technical/medical-sounding. The normal verb is simply water. The vast majority of several thousand NGram hits here for "feed and water the" will be using "water" as a verb, and juxtaposed with "feed" they'll also mostly mean "give drink to" (i.e. - not for washing).
Granted, "water" in this sense invariably does pair with "feed", and it's usually applied to animals rather than people. But I think unless you accept this word, you have to say we don't actually have a liquid equivalent to "feed" in common parlance.
Per John Lawler's answer here, and Benjamin's answer below, there was a time when drench would have been indisputably correct for OP's context. I wouldn't endorse such usage today, but it's worth noting the first definition in OED...
Verb 1 trans. To make to drink; to administer drink to; now spec. to administer a draught of medicine in a forcible manner to (an animal).
...and also worth flagging up several hundred written instances of feed and drench in Google Books.
The word slake is usually used in the context slake one's thirst
"Eat" is to "feed" as "drink" is to "feed", "drink", or nothing, depending upon the context.
"To feed" is a pretty versatile verb and can be used in several different ways. Some of the examples directly related to eating include:
- Transitive verb - to give food to: "I fed the food to the animal"
- Transitive verb - to provide sustenance to: "The grass fed the animals."
- Intransitive verb - to consume food: "The animals fed." or "The animals fed upon the food."
When talking about drinking rather than eating, you can find examples of people using the term feed, for meanings similar to 1 (e.g. "I fed the milk to the baby."), and drink for meanings similar to 3 (e.g. "The animals drank."). I do not know of an equivalent for meaning 2.
As others have offered, "water" can be used when talking of animals, and "hydrate" could be used at a stretch for humans but seems rather unnatural.
I think we should invent a word, and I vote for either "to libate", or "to embeverage" :)