Place the boneless, skinless chicken breasts evenly in the bottom of a 4- or 6-quart slow cooker.

In a medium bowl, whisk together the pineapple juice, BBQ sauce, ketchup, brown sugar, soy sauce, apple cider vinegar, ginger powder, and garlic powder until well combined.

Pour the sauce mixture evenly over the chicken in the slow cooker.

Cover and cook on LOW for 6 to 8 hours, or on HIGH for 3 to 4 hours, until the chicken is very tender and easily shredded.

Remove the chicken from the slow cooker and place it on a cutting board. Use two forks to shred the chicken completely. Return the shredded chicken to the sauce in the slow cooker and stir to coat thoroughly.

Optional thickening step: If you prefer a thicker sauce, mix the cornstarch and water together to form a slurry. Pour the slurry into the slow cooker (ensure the setting is on HIGH if possible) and stir constantly for about 5-10 minutes until the sauce has visibly thickened. Stir in fresh pineapple chunks if using.

Serve the Sweet Hawaiian Chicken hot on hamburger buns, over rice, or alongside coleslaw.