Turn on an unseen electric motor connected to a magnet under the table. The magnet creates a constantly changing magnetic field which causes a magnetic rod in the water to turn seemingly on its own accord, stirring the cup's content and forming a whirlpool.
Scientific Principle: Magnetic stirrer, mostly used in industry and in science labs
Needed Infrastructure: Electricity
Size in mm: height: 296
width: 700
depth / length: 450