Lay chicken breasts into your pot. Pour pineapple juice (and tidbits if desired for more texture) over the top.
In a bowl mix together brown sugar and soy sauce. Pour this over the chicken as well.
Put lid on and cook on high for 4 hours or 5-6 hours on low (recommended) until or until chicken is easy to shred with 2 forks and cooked to the correct temperature in the middle = 165F. degrees.
Slice or shred and serve over rice or inside tortillas for tacos. If shredding I would shred meat, submerge in liquid, and cover for an additional 20 minutes or so to soak up more of the juices.