I was making coffee cake muffins and the brown sugar dripped down into the cups. I filled the tins with water and stuck it back in the hot oven until the oven cooled. Then I took the tin out and washed with soap and water. The baked on sugar was removed with ease.
I even used the method with the bread pans. It works great when you spray them, it loosens the grease and gets rid of the greasy sticky feeling.