In a small bowl, combine the Tajin (1 tablespoon) and Granulated Sugar (1 tablespoon). Stir to combine. Add a little bit of water to one saucer. In the other saucer, sprinkle the tajin mixture in a round shape to mimic the glass that you're serving the drink in.
Dip the rim of each glass into the water and then into the tajin mixture. Set aside.
Thinly slice the Lime (1/2). Add the Fresh Pineapple Chunks (1 cup), lime slices and Fresh Mint Leaves (10) to a large cocktail shaker or pitcher. Using a muddler, crush the pineapple, lime and mint leaves until fragrant.
Add the White Rum (3 fluid ounce), Triple Sec (1 fluid ounce), and Pineapple Juice (6 fluid ounce). If using Simple Syrup (0.5 fluid ounce), add it at this point. Stir or shake until well combined.
Fill the glasses with ice.
Divide the drink into the glasses. Top off each drink with a splash of Club Soda (to taste). Make a slit in a chunk of pineapple and lime and affix them to the rim of the glass to garnish. Float a mint leaf in the top of the glass. Serve.