Pour in the sparkling mineral water, leaving plenty of room for the espresso.
Slowly pour the freshly brewed espresso over the sparkling water. The drink will foam, so pour carefully.
Stir gently and serve immediately.
Notes
Sparkling Water: I prefer sparkling mineral water, such as Topo Chico or S. Pellegrino, but club soda or seltzer water will also work.Espresso: Use freshly brewed espresso and coffee beans you enjoy. Since there's no milk to mask the flavor, the espresso really matters.Make it Sweet: Feel free to add your favorite flavored syrup to sweeten the drink, if desired.