Add chopped onion to the bottom of a slow cooker. Add chicken breast on top, then cover evenly with BBQ sauce. Top with crushed pineapple and bell pepper.
Cook on low for 7 hours (or high for 3), then remove chicken breast and shred with two forks. Return chicken to slow cooker and toss with sauce and juices. Set aside to cool.
Toss Power Slaw and cole slaw mix with cole slaw dressing. Divide into large compartment of 6 two compartment meal prep containers, then divide chicken breast into small compartments of containers. Add fresh pineapple garnish, if desired.