Technically that's only a problem if the value of alcohol as a currency is higher than its value as a good. If it's exactly equal then there's no way to "counterfeit" in the sense you're using the word. A ml of alcohol is worth exactly as much as itself, there's no way to convince someone that you're giving them alcohol that's worth more than it's actually worth. What's possible is that someone might produce impure liquor if it's easier.

Now, giving alcohol as a currency the value of alcohol as a good would mean having to buy, say, computer chips with hundreds or thousands of liters of alcohol. We might need some kind of token that stands for large quantities of alcohol, perhaps redeemable at certain places for the real deal.