Place chicken in the slow cooker. In a large bowl, combine the sugar, soy sauce, cider vinegar, ginger, garlic and pepper. Pour over chicken. Cover and cook on LOW for 5 to 6 hours or until chicken is tender.
About 20 minutes before chicken is done, cook rice according to package directions. Remove chicken to a serving platter, cut or shred into bite size pieces; keep warm. Skim fat from cooking liquid. Pour cooking liquid into a saucepan and bring to a boil.
In a small bowl, combine cornstarch and water until smooth. Gradually stir cornstarch mixture into cooking liquid and continue to stir until sauce is thickened. Pour over chicken and rice Garnish with chopped green onion, if desired.
Cook's Note: I have made this with and without thickening the sauce, it's entirely up to you.