What is Soda Water?

Soda water — and club soda, which is carbonated water with a light mineral addition — is CO2 dissolved in water under pressure. In mixed drinks it is a structural ingredient: it lengthens spirit or aperitivo, adds carbonation, and drops the perceived intensity of bitter liqueurs. Flat soda is still water; it no longer performs that role.

A highball is spirit plus soda (and ice). A Collins is a sour lengthened with soda. An Americano is Campari, sweet vermouth, and soda. A spritz is aperitivo, sparkling wine, and soda. None of these is garnish.

Neutral fizz. Club soda typically contains small additions of mineral salts (bicarbonates, sulfates) that register as a faint salinity. Tonic water is a different product: quinine, sugar, and citrus oils. Using tonic where soda is specified adds bitterness and sweetness the template did not account for.

Artificially carbonated water dates to the late 18th century; the highball as spirit-plus-soda is a 19th-century drink, associated especially with whiskey and later with gin. The Americano and the Venetian-derived spritz are the bitter, lower-proof versions of the same lengthening idea.

The Collins family (Tom Collins and its relatives) adds citrus and sugar before the soda, making a long sour rather than a plain highball.

Use a cold glass, plenty of ice, and add soda last; a brief stir is enough to integrate without driving off gas. Open a small bottle so residual carbonation lasts.

Do not substitute tonic unless the recipe specifies tonic — the quinine and sugar will rewrite the drink.