Gliders don't typically drink a lot of water, they get most of their liquids from the food they eat.
If you think they are dehydrated do a tent test, gently pinch their skin, when you release the pinch of skin it should go flat immediately. If it stays up 'tent like' then they are not well hydrated.
Try giving them juicy fruits to eat if you are carrying them in a pouch or offer plain pedialyte or diluted apple juice every hour or so until the pinch of skin goes down as soon as you let go.
What do you usually feed your gliders? are they on a good staple diet?
Sometime mine will do that if a light is on that is to bright for them they will just sit kind of frozen like and it seems like they are just starring off in space.
It takes them a few minutes after I turn off the light to get active and move around again...