I really wanted a carbonated cocktail. Partly because everyone mentions them in their "best of 2011"/"what's coming up in 2012" rundowns, partly because that's just how I do. I don't have a SodaStream or anything else actually intended for carbonating liquids, but I regularly carbonate fruit in my iSi cream-whipper by using a CO2 cartridge instead of a nitrous cart. Liquids are a little trickier because it's not an ideal-sized vessel for them, but is just about right to carbonate 1-2 servings. I've done homemade grape soda, for instance, which was almost entirely fresh-pressed Concord grape juice.
See, the benefit to carbonating a cocktail - or any other liquid - is that you're adding fizz without diluting anything. Normally to make that grape soda, you would either add club soda - watering down the juice - or cook the grape juice into a syrup and reconstitute it in club soda, changing the flavor significantly by cooking it. (Think of the difference between the way a fresh strawberry tastes and the way cooked strawberries taste in jam, sundae topping, pie, etc.)
Unfortunately for you, I did not note proportions while building this cocktail, I eyeballed it.
That may not matter since I used Charbay's Whiskey Release II, which isn't exactly a home bar staple.
But the basic idea is easy - grapefruit juice, maltiness, and bitters.
In order from most to least, I used:
Fresh-squeezed white grapefruit juice (1 grapefruit);
Charbay's Whiskey Release II (which is hopped, going well with the grapefruit);
Campari (about 1/4 ounce);
Peychaud's bitters (also about 1/4 ounce - which is a lot, yeah).
It's bitter, hoppy, and malty - sort of like beer, especially once you add those bubbles.