Sorry to sound like a broken record everyone but every time I see this question I have the same answer
Here is the run-down of the top 5 death reasons for sugar gliders:
1. Malnutrition and any malady stemming from it
2. Dehydration
3. Eaten / Crushed by dog or cat
4. Killed by another glider either directly or from infected bite
5. Exposure to extreme temperatures