Coffee culture around the world is always evolving, and in Japan, fans are singing the praises of sparkling coffee, AKA espresso tonic. In its basic form, sparkling coffee is simply tonic water poured over a shot of espresso with ice, which may sound odd, but soda-based sparkling coffee goes back as far as 1895, says Atlas Obscura.

According to Drink Trade, espresso with tonic specifically was invented by two Swedish baristas in 2007, and several years later, the concept showed up in niche, retro coffee shops in Japan. Long, hot summers in Tokyo gave widespread popularity to this refreshing, effervescent coffee that delivers cooling, fizzy caffeine on humid days.

Mixing tonic water with espresso creates a different flavor compared to soda-based sparkling coffees, since tonic water has a bitter zing from quinine. Tonic water also tends to contain sugar and sweetener that prevents sparkling coffee from becoming too bitter, and its citrusy flavor profile harmonizes with coffee's floral elements.

Popular spins on sparkling in Japan coffee include flavors like lemonade, lime, yuzu, orange juice, and even grape espresso tonic. There's also cola espresso tonic, though Japanese coffee houses tend to favor craft colas in their coffee rather than Coca-Cola or Pepsi, since a craft cola movement has been growing in Japan since 2018.