In a cocktail shaker, combine espresso, syrup, and soda water. Fill shaker with ice and vigorously shake until outside of shaker is very frosty, about 20 seconds. Divide between 2 coupe or martini glasses.
In a medium bowl, whisk cream and confectioners’ sugar until soft peaks just barely form. Spoon whipped cream over mocktail; smooth top with a spoon.
Crush 3 Oreos with your fingertips or place in a zip-top bag and crush with the bottom of a glass or rolling pin. Sprinkle crushed Oreos over half of whipped cream. Gently open enough of remaining 2 Oreos to attach to side of each glass.
