Sheep do drink water, yes. How much? How long is a piece of string? And how can a sheep make a monkey out of their owner...?
Sometimes they seem to get enough moisture from the grass that they eat; not sure where you are melholly but here we have had dewy mornings so the early morning grass is quite moist. Usually but not always they will drink after eating cake. Same applies after eating hay. Lactating ewes certainly need plenty of water, I have found that ewes with lambs kept indoors on hay + cake may drink as much as a gallon straight down twice a day. A newly lambed ewe will drink a couple of gallons - apparently the stuff she licks off the lambs is really salty!
And sometimes they like to laugh at us. I carried three 10L water containersfull out to my 16 lambing shearlings + 4 tups the other day - the third hot day on the trot and this field has no trough - expecting them to drink all that down and have to go back for some more. The blighters have still not drunk as much as one of those three containers.
With young lambs yes you must provide fresh clean cold water. Keep changing it, they won't drink it if it's dirty, stale and/or warm. They need to start drinking fresh water (and not from a bottle, something to do with the route the fluid takes if the head is raised or dropped) to get their digestions to develop properly, and certainly need to be drinking water to get them to eat any amount of creep, which they need to be doing before you can wean them off the milk.