For the House-made Vanilla Syrup:
Reduce the Nielsen-Massey extract to ½ cup. Combine it with the brown sugar and filtered water over medium heat to dissolve. Store in a squeeze bottle.
To Assemble and Serve:
Stir the Mexican Coca-Cola, espresso, and House-made Vanilla Syrup in a pint glass (you want to slightly cool the espresso). Add the ice and serve.