Realize that the requirement for an empty stomach is a serious one. While unconcious, should the contents of the stomach be expelled, then inhaled into the lungs (aspiration), a life threatening pnuemonia can develope. The stomach is never completely empty, there are always secretions (saliva, gastric secretions) present. Lungs can be damaged by the acidity of the stomach fluid, but the worst danger is when food particles are inhaled. Then you have the acid damage as well as the physical obstruction of the food particles. Very Bad. While this risk of aspiration is never zero, it can be greatly reduced by not eating or drinking. In all liklihood water would pass through the stomach very fast, but I doubt adequate studies have been done in cats to make this a safe assumption. In humans, there is evidence that water can be taken as late as 2 hours before surgery without increasing the risk, but again, I doubt cats have ever been investigated.
I only add this in, because I have noticed that when people don't understand why they are to do something, they might not do it or do it incorrectly out of misunderstanding. Fear not, the risk of anesthetic death is quite low in a young healthy animal. There might even be greater risk of death driving in the car on the way to the vet than there is from the surgery.