Experimenting with light and my cherished whiskey/bourbons

The idea of a paper towel or napkin to diffuse the light is a great idea for you - you could also experiment with adding more layers of paper towel to help tone down the flash power since it's so close to the subjects. Maybe different colored napkins to change the mood? Lots of options to play around with.

Cool concept though - it'd be a fun shot to hang in a bar once you have the light balancing nailed down.