A natural extract from the Bark of the Cinchona tree is found in many drinks like tonic water. It is a natural crystalline alkaloid that is sensitive to UV light and under a black light it glows blueish.
The flavor is distinctly bitter, and like most bitter foods some people love it while others just don’t get the appeal. Cinchona is so bitter that tonic water is always sweetened, and even sweetened the flavor is bitter. The distinct flavor works well paired with sour flavors like lemon and lime. The ultraviolet properties of Cinchona are quite remarkable. Turn on a black light with a bottle of tonic water around, and it’s like you’ve turned on a light bulb.
Try making ice cubes out of tonic water and using plain soda water for the drink to make a luminous cocktail. Not only will the contrast look remarkable, but the flavor of the drink will slowly change as the ice melts.