Sugar gliders in a 3+ colony will slumber together and can naturally keep their sleeping area very high in warmth and humidity. Adding humidity for sugar gliders is almost never needed. If you choose to experiment with a humidifier, look for a wet filter or a heated nozzle type. DO NOT USE one of the more modern ultrasonic styles as harmonics from the piezo speaker might be heard by tiny ears which could result in creating an awful and irreparable mental state.
The same goes for any sort of ultrasonic pest repeller devices. Dont use them if you have gliders. If mice and rats can hear it, well, ... If bugs can hear it, a harmonic can have the same effect on our furry friends.
I would swear that when I get near these devices, I cant hear them perse, but I can feel a pressure on my ears and it is annoying. I remember as a kid when we used to walk into Sears at the Richardson Square Mall, the electronics department was lined with televisions and I could hear and feel the extremely high ultrasonic screeches that these tubes put out. I would hate to subject such to my little beloved animals.