Instead of taking stuff away from a grave (grave robbing) you are adding to the grave site.
Usually taking the form of revenge; by having
lunch sat on their grave, tossing all the empty beer cans, wrappers, and crumbs over it. Then lighting up a few smokes flicking the
ash about and
grinding the butt into the headstone.
To finish you can then urinate and/or take a dump on the grave, using the flowers or cards to wipe with.