I'd count carbs for drinks and mixers but not the alcohol itself.
Beer and wine have some carbs, as do liqueurs, juices, syrups and sweetened mixers. Sugar free mixers and soda don't. Neither do gin, vodka, whisky etc. And lemon or lime juice are negligible in normal quantities.
Medical advice is that alcohol may lead to lower blood glucose, by inhibiting the liver's release of glucose when you need it because your blood glucose is dropping.
I was told, when I asked, that there wasn't any clinical evidence to support this. It may depend on how much alcohol you're metabolising, as well as your background blood glucose being on a downward trend. Good practice to check you're not going low after a night out.
My experience is that a diet gin and tonic, or whisky and water have no measurable effect on my blood glucose. Beer, cider or wine raise it.