Arrange the chicken thighs in a 6-quart slow cooker.
Whisk the soy sauce, pineapple juice, brown sugar, rice vinegar, ginger and garlic and pour it over the chicken.
Cover and cook on low until the thighs are tender, 4 to 4 1/2 hours.
Add the drained pineapple chunks and bell pepper and cook on high for 20 to 30 minutes.
Transfer the chicken, pineapple and pepper to a platter.
Whisk the cornstarch with cold water, stir it into the sauce and cook uncovered on high until glossy, 5 to 8 minutes.
Spoon the teriyaki sauce over the chicken and serve with rice.