If he gets into something soapy or with other chemicals you would need to rinse him off with slightly warm (bath temperature) plain water.
To dry your glider - use a a towel and wrap him up to absorb most of the water then keep him in a bonding pouch on you to keep him warm until he is fully dry. He will groom away the remaining water.
NEVER use a hair dryer or any blowing air to dry a sugar glider. Their ears have very thin tissue and the blowing air on wet skin would cause damage to their ears. It would be like the severe chapping your lips feel when you are out in the wind and you lick them to make the dry skin feel better - only to have the wind dry them out again causing them to painfully crack. The problem is this chapping of a glider's ears can cause permanent damage and even loss of part of their ears.
The biggest danger of falling into a toilet is that the glider would be unable to climb out of the slick wet bowl and he would eventually tire out and drown.