Place the chicken breasts into the base of the slow cooker. Pour the chiptole peppers, crushed pineapple with juices, and chopped onion over the top. Stir gently to combine.
Squeeze and zest the lime and orange, then stir gently to combine.
Set the slow cooker on low and cook for 8 hours. At the end of the cooking cycle, shred the chicken into the sauce.
Warm the corn tortillas or taco shells and spoon the shredded chicken with some sauce onto the tortilla. Top with sliced pineapple, chopped cilantro, and cotija cheese. Enjoy!