All you need is
1 piece of card board
2 coffee mug
3 unsuspecting person
Step 1: Observation
Try to figure out when the person leaves his/her desk and comes back this may be helpful in the future.
Step 2: The Fun Part
When they leave their desk get thier coffee mug and put the cardboard on top untill it is suctioned on.
Then turn it over and place on the table (warning:before perfoming this trick you should practice it a few times) slide the cardboard carefully away leaving a full coffe mug upside down.
Step 3: Results
when the person comes back they will think the coffee mug is empty, but little do they know when they pick it up................
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