How about something along the lines of vodka and coke???
That way you get a "proper" drink, as opposed to drinking just shots. Then if you have coke zero or similar, that has no or few calories, you can then enjoy a couple of drinks as normal, but with fewer calories.
You will have to find out the amount of calories in a shot "of your choice" mind you, but really, how many can there be in just 25ml ?????