Wine: An Efficient Choice… Usually
Unlike beer, wine is much easier to gauge from an efficiency standpoint. Most wine is near 100%, meaning that almost all calories are from alcohol. Beyond that, there is one important distinction to determine efficiency and calories: not red wine vs. white wine, but rather dry vs. sweet. Dry wine ferments almost all of the grape juice, leaving little residual sugar (related blog post coming soon). So, dry wine has few empty calories. Sweet wine, however, has either residual or added sugar, therefore more calories and lower efficiency. Note that anything labeled wine product is probably not a great choice for efficiency, or anything else, for that matter.
Winemakers publish ABV (alcohol by volume) but not calories. So, to be sure, stick with traditional varietals and blends, which all tend towards dry. Although the list is long, below are some examples: