Warning: Proceed with caution. Coffee machines are known to be a security risk.
Step 1: Disable the coffee machine's power cord. Use a black marker to draw a diagonal line through the cord, making it look like a "Do Not Use" sign.

Step 2: Place a sticky note on the coffee machine's control panel. Write "Do Not Use" in bold letters, making it clear that the machine is not to be used.

Step 3: Call the IT department and report that the coffee machine is "broken". When they send a technician, pretend you have no idea what you're talking about.
For more advanced coffee machine sabotage techniques, click here.
This section is dedicated to the late, great, coffee machine saboteur, John.