To demonstrate Newton's third law of motion.
Start by placing the metal top on the block of wood in the tupperware container. Hold the top by the little metal ring and pour water into the top. Continue to pour the water in as the top begins to spin.
Make sure to have enough water on hand to be able to keep the top spinning for more then a few seconds. Also make sure the top is inside the tupperware or water will be everywhere.
The potential energy of the gravity on the water is converted to rotational energy as the water is pushed out of the top and causes the top to spin the opposite direction. This is the same idea as why a rocket gets propelled.