How many carbohydrates in 190 proof ethanol?

None. Ethanol contains 7 calories per gram, but since ethanol is boiled off (distilled) from the sugary MASH that creates it, there are no sugars or other carbohydrates left. This is not only true of ethanol, but all unflavored liquor. In fact, chronic alcoholics go through the same process of ketosis sought after by low-carb dieters; they're subsisting on ethanol calories and their blood sugar is near rock bottom.