Place the chicken breasts at the bottom of the crockpot. Season with salt and pepper.
Mix the Sauce: In a medium bowl, combine the pineapple juice, brown sugar, soy sauce, and minced garlic. Stir until the sugar is dissolved and the ingredients are well mixed.
Add the chopped bell peppers, onion, and pineapple chunks over the chicken in the crockpot.
Pour the pineapple juice mixture over the chicken and vegetables.
Cover the crockpot and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is fully cooked and tender.
Serve the sweet Hawaiian chicken over cooked white rice. Garnish with chopped green onions and sesame seeds if desired.