Bring in snacks like cookies, crackers, something that comes in a box. Carefully open the contents with a box knife and pull out the plastic bag insert and empty the contents. Next, fill up the box with shredded paper and a few items that might give it some weight like old CD's or floppy disks.

Carefully reseal the box with glue and place it in the break room. Check to see how long it takes a coworker to be tempted into opening the box.