As Happy as a Squeezed Snake

To add the fluid into the gas station windshield washers, first you need to squeeze a snake. The manufacturers of the washer fluid squeeze the snake which allows the washing fluid to come out of a snake. This takes off a lot of weight from the snakes, making them very happy that they have been squeezed dry.

"Dude what are you doing, Why are you smiling so much?"
"Dude i'm as happy as a squeezed snake!"