The "fire in the hole" would be funny if they were in the middle of nowhere (i.e. nobody else would be affected), and then smashed a gallon jug - of nitroglycerine.
Perhaps I'd best explain. "Fire in the Hole" was a prank where the perp would order food at a fast food Drive Thru, then when the window clerk is doing something else (ie, making change), the perp would yell "fire in the hole!" and throw a full beverage cup through the window at the clerk. Apparently this was the height of teenage humor a few years ago.
"Gallon smashing" is the prank referred to in the OP, where the perp smashes a gallon bottle of milk or juice and pretends to slip in it. Two totally different pranks, both involving containers full of liquid and a pathetic sense of "humor".