Mix the coffee liqueur, creme de cacoa, vodka, and espresso in a small pitcher. Cover the pitcher with plastic wrap and place it in the freezer until the mixture is very cold, about 3 hours.
Meanwhile, rub the rims of 8 Martini glasses with the orange wedge. Dip the rims in the sugar crystals to coat lightly. Place the glasses in the freezer.
Add the ice cubes to the vodka mixture and briskly stir the mixture until the ice begins to melt. Strain the mixture into the prepared glasses, and serve.
For kids, serve hot cocoa with sugared rims.