Lightly grease the slow cooker with cooking spray.
Place the chicken breasts in the bottom of the slow cooker.
In a bowl, whisk together the soy sauce, brown sugar, honey, garlic, ginger, rice vinegar, and sesame oil.
Pour the sauce evenly over the chicken.
Cover and cook on LOW for 5 to 6 hours or HIGH for 2½ to 3 hours.
Remove the chicken and shred it using two forks.
Whisk together the cornstarch and water until smooth.
Stir the cornstarch slurry into the sauce in the slow cooker.
Cover and cook on HIGH for 10 to 15 minutes until the sauce thickens.
Return the shredded chicken to the slow cooker and toss until fully coated.
Garnish with sliced green onions and sesame seeds before serving.