>>392787960
I don't know how to tell you this but all alcohol is alcohol. Rum is actually one of the LEAST calorific beverages: What you're looking for is something with just alcohol. 
No extra sugars (wine, ciders, liquors)
No carbohydrates (beers, lagers, etc)

What you are in fact looking for is rum, whiskey, vodka, etc. All unmixed of course. If you really can't drink it straight water it down.