This is a wonderfully simple plot that creates a really puzzling effect. A regular, ungimmicked coffee cup is shown and a large sponge ball is tipped out from inside. The cup is clearly shown to be otherwise empty and both of the performer's hands also have genuinely nothing in them.
The ball is placed into a pocket, both hands again being shown to be empty. The inside of the coffee cup is displayed and then inverted mouth down onto the magician's hand. A snap of the fingers and when the cup is tipped backwards, the ball is found impossibly to be back underneath.
[Note that this is not sufficiently angle-proof for most close-up situations. It works wonderfully for a parlor environment, though.]
1st edition 2026, video 7:13.