Hi Urabeth,
I just replayed that part. After showing the bottle to the bartender and his saying that only Martyr drinks it - Move the cursor to the mug between the 2 sailors and it will be active. It is dark and might not be able to see it. Might need to raise the brightness of the computer here. Click on it and Jazz will walk to the mug and tip it. A fight ensues. Immediately place the cursor on the cigar box and when it changes to an active cursor - click.
I just saved the game here and if you need it just tell me, OK.
Hope that helps!
MaG