Combine Ingredients in Slow Cooker: Place the chicken breasts (or thighs) in a 5-quart or larger slow cooker. Add the finely chopped pineapple, minced jalapeño, minced red onion, minced garlic, salt, chili powder, cumin, paprika, dried oregano, crushed tomatoes, water, and lime juice.
Stir all the ingredients together well, ensuring the chicken is evenly coated with the spices and sauce.
Cook: Cover the slow cooker with its lid and cook on the HIGH setting for 4 hours, or on the LOW setting for 6 hours, until the chicken is very tender and easily shredded.
Shred Chicken: Carefully remove the cooked chicken from the slow cooker and place it on a cutting board. Using two forks, shred the chicken into bite-sized pieces.
Return the shredded chicken to the slow cooker and stir it back into the pineapple-infused sauce. Allow it to soak up the flavors for an additional 10 minutes.
Assemble Tacos: Warm your tortillas. Spoon the delicious pineapple chicken mixture into the warm tortillas. Top with your favorite garnishes such as sour cream, sliced avocado, fresh cilantro, or pickled onions. Serve immediately.