Is your water fresh? Especially the males do need water but obviously you can't force them to drink it. Are your goats dairy goats? My goats are dairy goats and would prefer to just be in the barn eating hay. But I lock them out on pasture and they are eating grass more and more. Goats do prefer browse (weeds, shrubs, etc) over grass but if grass is what you have, then that is what they have to eat.
You could try putting some molasses in the water if they really aren't drinking enough.
the first summer we had our goats i never saw them drink a drop of water out of the bucket. ever.
but then i realized how much they went thru in the winter..and also our dairy gals, when in milk, drink a LOT.
also they might be fussy about what bucket and how clean it is. if our water gets dirty (for instance if the ducks toddle over and use it) we have to dump it out and start over. and then remember to hang the bucket up to keep the ducks out. and heaven forbid the dogs slobber in it. sheesh!
my goats drink the most when I am refilling w/ nice cold fresh water.... They will gather around then.... They do drink during the day but enjoy the daily fresh water the best...
My goats arent the best w/ eating grass.. I just let the horses into thier field to mow it for me.. They do love getting out to get the weeds and shrubs though...
My goats have their days. Sometimes the bucket is half gone during the day. Other times it looks hardly touched. I find if I top dress their grain with minerals they drink more.