COmbine the ketchup, soy sauce, rice vinegar, honey, Sriracha, sesame oil, ginger, garlic, black pepper, and 1 cup of water in the slow cooker. Mix well.
Set the chicken thighs on top of the sauce and spoon sauce over top of the chicken thighs.
Cook on low for 7-8 hours or on high for 3-4 hours.
Add the broccoli and peppers to the slow cooker, spoon sauce on top of them, and cook on low for an additional hour.