This is a variation of the Lota Bowl, (concept by Sam Dalal) with a more appealing and natural presentation for a modern comedy act.
 
In effect, after the end of his first trick, the performer rewards himself with a shot of scotch, rum, or whatever his favourite spirit! He pours the drink out of a hip flask, shaking out the very last drop, it’s the very last peg, and tips it down.
 
After the next effect he repeats the ritual, and magically, one more last peg has appeared in the flask. Again he shakes out the last drop, before placing the flask aside.
This is repeated over and over again, up to a dozen times. As a running gag, it gets funnier and more mystifying with each repeat.
 
If you are the partying type, you could even use this as an attention getter at any regular party.