Then they get bent out of shape the next time they come to their spot and there is no trespassing signs.
When I go catfishing at night, I bring plenty of snacks and smoke about a pack of cigarettes. I put every butt in a soda can, every snack wrapper in the bag I got when I bought them... I'm pretty lazy myself, but its not hard to clean up if you don't make a mess in the first place.