Add both for flavoring. Get it as cold as you can stand it without getting brain freeze. Plug your nose HARD. Take a very deep breath with the container held well away from your mouth and with your nose plugged, then chug as much per breath as possible. Take a tiny sip of something sour (this sounds freakish, but I used pickle juice so there would be nearly zero sweetness involved, unlike, say, lemon juice) after each chug. Lather, rinse, repeat.
Licking a boullion cube in between might help, too. Note that the pickle juice is salty as well as sour.