Most of the popular budget or flimsy style of cages have the lift up "guillotine" type of access doors on them. These are inherently dangerous to sugar gliders. The door can slam down on your beloved pet.

Here are some fixes:

How to modify budget cage doors
Ebay cage doors

Here is a wonderful modification for those of you who have small and/or guillotine cage doors. It can be done on any cage, even the flimsy wire ones.

Glider Mansion - Corner Aviary Door Project