Tonic water contains a bitter ingredient called quinine and a dash of sweetener to offset the bitter taste. Whether you are mixing an alcoholic or nonalcoholic drink, adding tonic water can counterbalance sweet flavors in the drink. Just be careful as you open a bottle of tonic water — you can make a mess if you don’t do it correctly due to the extreme fizziness of the water.
Chill the bottle of tonic water thoroughly — for at least four to six hours.
Remove the bottle of tonic water from the refrigerator carefully without shaking or jostling the contents.
Place the bottle on the counter. Slowly begin to twist the cap off the bottle. Stop twisting as soon as you hear the first fizz, and let the tonic water rest for about 10 seconds.
Continue twisting the cap off slightly and then stopping to let the water rest. You should hear fizzing each time you twist the cap more.
Watch the water level. If it begins to rise in a threat of overflowing, quickly tighten the cap completely to prevent a mess. Let the water rest for about one minute and then start untwisting slowly again.
Twist the cap more quickly as you reach the point where you no longer hear a fizzing each time you twist. This tells you that you have released the bulk of the carbonation and the threat of overflow is receding.
Remove the cap completely after all fizzing stops.
Pour out the tonic water slowly, and recap the bottle if any tonic water remains in the bottle.
Keep a towel nearby to clean up if the bottle overflows.
References and ResourcesHomeBrewUnderground: Non-Alcoholic Drinks
The Kitchn: Fizzy Waters - What's the Difference?