In a large bowl, combine the sugar, soy sauce, cider vinegar, ginger, garlic and pepper.
Pour over chicken.
Cover and cook on low for 4 to 5 hours or until chicken is tender.
Remove chicken to a serving platter; keep warm.
Skim fat from cooking liquid or put it through a mesh strainer.
Place liquid in a saucepan and bring to a boil.
Combine cornstarch and water until smooth.
Gradually stir into liquid and stir until sauce is thickened.
Serve over rice and garnish with green onion and sesame seeds.
Note: I halved the recipe and it still worked fine in my crock pot. I kept the amount of sauce the same and it was done in about 2 1/2 hours.
How to Convert to Instant Pot: Cook on High Pressure for 10 minutes with a quick release. Remove the chicken and shred. Add the sauce ingredients into the Instant Pot and turn to saute, allow sauce to thicken. Pour over shredded chicken.