Prepare the Chicken:
Place the boneless, skinless chicken breasts into the bottom of the crockpot.
Make the Sauce:
In a mixing bowl, combine the pineapple juice (from the canned pineapple), soy sauce, brown sugar, ketchup, apple cider vinegar, garlic powder, ginger, and black pepper. Stir until the sugar is dissolved and the ingredients are well combined.
Pour the Sauce Over the Chicken:
Pour the sauce mixture over the chicken breasts in the crockpot. Add the pineapple chunks on top of the chicken.
Slow Cook:
Cover the crockpot and cook on low for 4-6 hours or on high for 2-3 hours, until the chicken is tender and easily shreds.
Shred the Chicken:
Once the chicken is cooked, remove it from the crockpot and shred it using two forks. Return the shredded chicken to the sauce and stir to coat.
Optional Thickening:
If you prefer a thicker sauce, whisk the cornstarch with a tablespoon of cold water to make a slurry. Stir this into the sauce in the crockpot and cook on high for an additional 10-15 minutes to thicken.
Serve and Enjoy:
Serve the Sweet Hawaiian Crockpot Chicken over steamed rice, in wraps, or on buns for sandwiches. Garnish with chopped green onions or cilantro, if desired.