Don't drink anything with sugar in it as a mixer. Alcohol in and of itself is a sugar. Lot's of people like to mix Coke or 7-Up or something sweet in their booze. Don't. This will bring on heavy hangovers.
If you mix a juice in, use grapefruit or cranberry, not orange juice. And before you go to bed, pop down 2 or 3 pain relievers of your choice. This will stop the swelling in the brain brought on by the alcohol and inhibit the livers ability to process the extreme amount of sugars loaded up from the booze and dispose of them.
I prefer my vodka on the rocks as long as it isn't rotgut stuff. No extra calories from some shitty mixer.