Which carbonated beverage is flavored with quinine and often used as a mixer? The answer is tonic water.
Tonic water is a carbonated soft drink containing dissolved quinine, the compound responsible for its characteristic bitterness. Modern versions are usually sweetened and may include citrus flavorings, so they taste far milder than the medicinal preparations that inspired them.
Quinine came from the bark of Cinchona trees in South America and was used against malaria. In 19th-century British India, people mixed bitter quinine with soda water and sugar to make it easier to drink. Adding gin eventually produced the gin and tonic, now its best-known cocktail use.
Tonic water is not the same as seltzer or club soda. Those are carbonated waters without tonic’s defining quinine bitterness, while ginger ale is flavored with ginger. Tonic is also not a reliable substitute for medicinal quinine: commercial drinks contain much less quinine than therapeutic doses and are primarily refreshments or mixers.