Step 1: Building It
Drill a hole for the stopper. The diameter will depend on the exact stopper you use – I used a 5/16 bit. Be careful drilling this as you can easily buckle the metal – I started with a small bit and worked slowly up, putting almost no pressure on the drill head. The hole needs to be as neat and round as possible.
Insert the water pistol stopper. And that's it. You are now prepared for any situation that demands a small, warm cocktail.
If only I could figure out a way to ice it...