What's the Difference Between Tonic Water, Club Soda, and Seltzer?

Club soda on the rocks ... or is it?. (Photo: Marco Verch Pro [CC by 2.0]/Flickr)

My recent obsession has been beverages. It all started with limoncello. Now, I’m creating cocktails at home and ordering unusual cocktails when I'm out. I’m buying shrubs and making my own. I’m also diving into many styles of beers that I’ve never tried before and hounding my beer-brewing friends to let me try everything they make.

While playing with drink recipes, I realized I have never explained the difference between club soda, seltzer water, and tonic water. People wonder what is in each mixer and if they’re interchangeable. They all look the same—can they all be used the same way? Here's what to know.

Club Soda

Club soda is carbonated water that has added minerals like potassium bicarbonate and potassium citrate to enhance the flavor. It can also have added sodium, but not all club sodas contain sodium.

Seltzer Water

Seltzer water is also carbonated water, but it doesn’t have any additives, such as sodium. You can purchase flavored seltzers, usually in a citrus flavor, but plain seltzer is simply water that is carbonated.

Tonic Water

Tonic water is the least water-like of the three. It does contain carbonated water, but it has quinine to give it a bitter flavor and also a sweetener, usually high-fructose corn syrup or an artificial sweetener to make a “diet” tonic water. It’s more of a soda than a water.

Club soda and seltzer water are interchangeable in beverages, but tonic water will add sweet and bitter to whatever you’re creating. You shouldn’t substitute tonic water for club soda or seltzer water, nor should you substitute club soda or seltzer water for tonic water.

There you have it—a simple explanation about these three common drink mixers. Did you already know this, or did I teach you something?