Espresso tonic started as an experiment at Koppi Roasters in Sweden back in 2007, and it's since become a genuine specialty coffee staple rather than a passing novelty. The idea is simple: bold, fresh espresso poured over quality tonic water and ice. The result is refreshing, low in calories, and shows off a coffee's brighter side in a way a milk-based drink never will.
Choosing your beans
Light to medium roasts work best, ideally with fruity, floral or citrus character, exactly the notes tonic water's bitterness and carbonation are built to complement. Ethiopian coffees are close to the gold standard here, both washed and natural processed varieties tend to work brilliantly against tonic.
Pulling the espresso
Standard specialty espresso parameters apply: 18 to 20 grams of ground coffee, extracted to 36 to 40 grams of liquid over 25 to 30 seconds at around 93°C and 9 bars of pressure, a 1:2 ratio. Nothing unusual here, the espresso just needs to be genuinely good, since it's doing most of the flavour work in this drink.
Building the drink
Combine a fresh double espresso, 40 to 50ml, with quality tonic water at roughly a 1:3 to 1:4 espresso-to-tonic ratio, poured over ice. Pour the espresso in last, over the tonic and ice, so you get that layered look as it settles.
A few worthwhile additions
Citrus: a twist of orange or lemon peel lifts the drink further, particularly with a fruit-forward Ethiopian shot.
A touch of syrup: a small amount of a simple, clean syrup, not overpowering, can round out a shot that's leaning too bright or acidic on its own.
Saline solution: a small pinch, roughly a 1:5 salt-to-water ratio added a drop at a time, is a trick some baristas use to tame excess acidity without adding sweetness.
The takeaway
Espresso tonic is one of the simpler specialty drinks to make well, mostly because it doesn't hide a mediocre shot the way milk can. Start with good beans, pull a genuinely good espresso, and don't skimp on the tonic water, the drink is only as good as its two ingredients.
