Caffeine. Bubbly. It's about time you two met.

No, not that kind of bubbly. But we like where your head is at.

We're talking about tonic water, the latest ingredient to show up in trendy espresso drinks. Unexpected? Definitely. But after one taste, we swear you'll be wondering: Where has this been all my life?

The truth is, espresso tonics—sometimes called caffe tonics or black tonics—have been around for a while. They're on menus in trendsetting cities like Tokyo, Toronto, Melbourne, Stockholm, Helsinki and Berlin. And now they've touched down in San Francisco thanks to Kevin Bohlin, founder of 7-month-old Saint Frank Coffee shop, who discovered them through a Swedish micro-roaster at an international barista competition.

The concept is as simple as it sounds: A long shot of espresso is poured over a fizzy glass of artisanal tonic water on ice. But the result is surprisingly complex—a sweet and citrusy, creamy and effervescent, so-beautiful-you-can't-help-but-Instagram-it concoction with a Guinness-style frothy head. It's a cup of coffee and a palate cleanser all in one.

How to Make Your First Espresso Tonic



Pulling one off actually takes some know-how, Bohlin says: "First off, not just any combination of espresso and tonic will do." He tasted through eight brands of tonic—some too lemony, some too bitter—before finding a just-right fit in Fever Tree. The second secret, he says, is pulling an espresso shot with a clean, non-bitter profile that complements the tonic. "We use a single-origin Central American espresso—quintessentially clean and bright—and pull it much lighter to enhance the citric, fruit-forward quality."

Finally, order matters. Start with six ounces of tonic water on the rocks, then slowly pour the two ounces of espresso on top. "If you pour them too fast or in the wrong order, it'll overflow," Bohliin says.

Somewhere, a regular iced coffee weeps.