Here's what I found. It says 64 calories, and you're right, no fat, no carbs, no protein, it's all been converted to alcohol sugar. The south beach good fats good carbs guide I have says you can have it on a limited basis in Phase 2 and 3, but no alcohol at all during phase 1. Hope this helps.
http://www.fitday.com/WebFit/nutriti...ges/Vodka.html