In a large zip-top bag, combine the pineapple juice, garlic, vinegar, lime juice, tomato paste, chili powder, salt and cinnamon sticks. Add the pork loin and rub to coat. Refrigerate for 4 hours or up to overnight.
Preheat the oven to 375 degrees F. Remove the pork from the refrigerator and let sit at room temperature for about 15 minutes.
Remove the pork loin from the bag, let excess marinade drip off and transfer the pork to a roasting pan. Roast until a meat thermometer inserted into the center of the loin reads at least 145 degrees F, about 45 minutes.
Transfer the pork to a cutting board, and let rest for 10 minutes. Slice into 1/2”-thick rounds, then slice those rounds into strips.
While the pork roasts, make the pineapple jalapeño salsa.
Assemble the tacos starting with a few strips of the pork, then the salsa, sour cream and cilantro.
*Pineapple jalapeño salsa: Combine 1 cup diced fresh pineapple, 1 tbsp diced jalapeño, 1/2 small diced red onion, 1 tbsp lime juice and 1/3 cup lightly packed chopped cilantro.