So we've got beer (wheat and/or hops) and rum (sugarcane). What other crops could we make drinks out of? We've got potatoes, carrots, pumpkins, and melons. Potatoes certainly could be used to make vodka. The others might be used to make some sort of wine.
But we've got all this alcohol, and doesn't it work well as a fuel? How about we can empty a booze barrel into a cell instead of a mug, run it through an extractor (still), and use the ethanol cells to fill fuel cans?
What else could we use to make ethanol? How about plantballs? They could break down and ferment in a booze barrel too, giving more extractable fuel. Of course, you wouldn't be able to drink it without killing yourself... Or maybe you could macerate a log, throw in the wood chips, and get wood alcohol.
The overall idea is that the net energy yield for the same ingredients would be higher with this method than with the traditional biofuel method due to the time investment in the fermentation.