That's why we use diet lemonade mix in our margaritas.
The only calories you get are from the alcohol, which is IIRC around 100 per.
Most mixes or regular soft drinks are gonna add between 100 and 200 more cals per drink.
....and a must reiterate about the added cals in cinnamon flavored stuff like Fireball- you are consuming the sugar cals in the drink just like if you mixed it with soda.