I think Kevin1 is right. If the recipe calls for Bourbon Whiskey, use a bottle of something that says "Bourbon Whiskey" on the bottle. I do not drink Whiskey but cook a sauce using Bourbon Whiskey. I bought a half-pint of Wild Turkey for this purpose. The recipe only calls for 1/4 cup, so this quantity is enough for four separate sauces. The cost of getting a half-pint of the right ingredient isn't going to break anyone's bank account, I don't think.

Further, if the recipe calls for Cognac, use Cognac. True, Cognac is a brandy, but not all brandy is Cognac. Cognac is a superior brandy made only in a specific small region in the world and according to specific growing, harvesting, fermenting, and distillation procedures dictated by law. My recommendation is to use V.S.O.P. Cognac when cooking with Cognac -- Very Special Old Pale -- which is superior to V.S. Cognac or simply designated Cognac. Since invariably you are only using about 1/4 cup at a time, it doesn't cost much to make this kind of investment in quality.

Also, the various hard liquors are not interchangeable in cooking. Don't use Cognac where Bourbon Whiskey is called for; don't use Bourbon Whiskey where Cognac is called for. These provide quite different tastes to the sauce or dish being prepared. If this weren't the case, why wouldn't all recipes call for the cheapest mass produced Vodka available?