Lightly spray a 3-4 quart slow cooker with cooking spray. Place chicken in the cooker. In a small bowl stir together the stir fry sauce and the water. Pour over the chicken.
Cover and cook on low for 6-7 hours or on high for 3-3 1/2 hours.
Transfer chicken to a cutting board; using two forks, shred the chicken and return to slow cooker (the chicken will be so tender, you probably can just stir it around in the slow cooker to shred it). Stir in the broccoli slaw. Cover; let stand 5 minutes.
Serve chicken mixture on top of warm whole wheat tortillas.