No good deed goes unpunished.
Just tell him your closed. If he gives you a hard time, tell him you’ve cleaned the equipment already. When I worked in a craft store, we had people that would bang on the door after we were closed. You should hear some of the sob stories they came up with!
As some may know, California is banning plastic straws. I was in a large national coffee shop getting an iced tea. The barista handed me a cup with a drinkable lid. I said “Oh, a Sippy Cup.” I was informed in most frigid tones “We do not refer to these as ‘Sippy Cups’, these are drinkable lids.” I told him, “I have raised kids and grand kids, THIS is a Sippy Cup.”