Place the chicken chunks in the bottom of the slow cooker.
Add the sliced red and green bell peppers on top of the chicken.
Pour the entire can of pineapple chunks along with their juice into the slow cooker.
In a small bowl, stir together the ketchup, rice vinegar, brown sugar, soy sauce, and garlic powder until smooth.
Pour the sauce mixture over the chicken, peppers, and pineapple.
Stir gently to coat everything evenly.
Cover and cook on low for 6 hours or on high for 3 to 4 hours, until the chicken is cooked through and tender.
Stir once more before serving over cooked rice.