I can not help you with this problem since I'm not too experienced with their medical needs yet. I'm still learning.
However, just to brainstorm: Do you wear perfume? Possibly excessive chemicals are bothering her and making her sneeze? Maybe there is something you encounter commonly or work with and it bothers her? A friend of mine specifically puts perfume on her inner wrists and when she forgets to wash it off, her gliders get irritated by it and sneeze. They never sneeze excessively otherwise. I would play around with that to see if it could possibly be it.
Either way, I just wanted to leave a little note for you to keep in mind: The thing with exotics is that by the time they are showing symptoms, its usually too late for the problem to be corrected. Sugar gliders especially are known for hiding symptoms.
This isn't always the case, but don't assume it is.
So, its your call in the end; if you really feel all the sneezing is abnormal, then I would get it checked.