Thoroughly wash and scrub the pineapple. Peel the pineapple, reserving the peels and core. Cut the pineapple fruit into chunks for another use.

In a large glass jar or food-grade bucket (at least 1.5-gallon capacity), combine the pineapple peels and core, piloncillo (or brown sugar), and cinnamon stick.

Pour the filtered water over the ingredients, ensuring everything is submerged. Stir gently to dissolve the sugar.

Cover the jar loosely with a clean kitchen towel or cheesecloth, securing it with a rubber band. This allows air circulation while keeping insects out.

Place the jar in a warm spot away from direct sunlight for 24-72 hours. Fermentation activity will begin, indicated by small bubbles rising to the surface and a slightly yeasty smell.

Taste the tepache after 24 hours. It should be sweet and slightly fizzy. Continue fermenting until it reaches your desired level of fizziness and tanginess. Do not over-ferment, as it can turn alcoholic or vinegary.

Once fermented to your liking, strain the tepache through a fine-mesh sieve into a clean pitcher or bottles. Discard the solids.

Chill the tepache thoroughly in the refrigerator before serving. Enjoy it over ice, perhaps with a squeeze of lime.