There are several options here:
If the clink sound is hear and a coin is inside the glass he might have used a muscle pass from the hand not holding the coin.
If the clink is heard but there's no coin in the glass, he did a muscle pass with the hand that's holding the glass.
If you hear the clink and he quickly moves the glass down to the table to apparently drop the coin that appeared he might be using a muscle pass with the hand that is holding the coin and then a Hand Ping Chen with the other hand (or possibly the same hand, it would just be a modified Hand Ping Chen). Or was it Chen Ping Hand (or possibly a modified Chen Ping Hand)? I can't remember which one it is but it's the one where the coin comes out of the hand.