Before you leave, take some raw ground beef, open it from the wrapper and start stashing it in above the ceiling tiles, and in the back of cupboards.
In the back of desk drawers. If you really feel daring, take a poop in the boss's desk drawer.
Back in the day, you'd pour a couple two liters of coca cola into his gas tank.
However, everything has locks.

PS, if you don't want to poop in the boss's desk drawer, then consider taking a shoe box full of kitty litter droppings to work...and, well... You get the idea.

Now go!