Step 1: Materials:
-a bic pen, or a very similar style of pen with a cap
-coffee(and a coffee machine, you silly goose!)
-scissors for cracking open the pen
-a gluegun to make it watertight
(a funnel and tape turned out to be very handy for filling the pen with coffee)
and last but not least, a victim!!! >:P
Step 2: Taking Apart the Pen:
just throw out the ink tube and ballbearing ink system, or keep them for another prank!
if you do need to use scissors, insert the blades in the small crack and pull away from the body of the pen.
Step 3: Making the pen Watertight:
take the gluegun, and put glue on the end of the cap and the back end of the pen(the end that doesnt go into the cap when the pen is closed). this will keep coffee from leaking out of the little holes there. IMPORTANT!!!: test with water before you use it! if it leaks before the person opens it they will not pick it up and spill coffee everywhere! also, you can brew your coffee while doing this.
Step 4: Adding the Coffee:
for this, i used a small funnel taped to the open end of the pen. this really helped keep things clean. just in case, do this step above a sink. just pour the coffee in until it is full.