My male sugar glider has been drinking about 20 ml of water a day and eating most of his food. Is this normal?? He's on the SGS 2 diet. He has also been waking up during the day. I've assumed this is because he's lonely and I'm up during the day. I have another sugar glider but she's still too small to introduce yet.

Depending on how much water you add while blending your vegetables, there might not be enough which pushes him to drink more.
I would increase the portion until there are some leftover in the morning, the advised 1 tablespoon has never been enough for my gliders, and they tended to wake up for a snack during the day until I increased the portion to 2 tablespoons of SGS2.
Be aware that the online version of the diet has some mistakes, for example the official diet calls for 1TBS linseed and 1TBS of either oatmeal or wheat germ for 1lbs of fruits/veggies.