I love tonic water. It adds so much to a cocktail—bitter, sweet, sour, salt—all packed in one neat little bottle. My favorite part about making tonics is the fact that as long as you have the essential ingredients, you can add any other flavors you can dream of to make it unique and beautiful. The basic essential ingredients to any tonic are quinine, sweetening agent, citric acid, salt and of course a liquid (more often than not water will be the liquid).