What is the main difference between Club Soda and Tonic Water?

The main difference between Club Soda and Tonic Water lies in the presence of quinine, a compound found in tonic water. Quinine is derived from the bark of the cinchona tree and has historically been used to prevent malaria, but it is also responsible for the distinctive bitter flavor of tonic water. This makes tonic water a unique mixer, primarily used in cocktails like the gin and tonic.

In contrast, club soda is simply carbonated water that may have added minerals for a slight taste, but it lacks the bitterness associated with quinine. This absence of quinine means that club soda is a more neutral mixer, allowing it to complement a wider variety of drinks without imparting a pronounced flavor. Thus, the presence of quinine in tonic water is what distinctly characterizes it compared to the more neutral and simpler profile of club soda.