In a medium bowl, whisk together the sugar, soy sauce, cider vinegar, garlic, ginger, and pepper. Pour over chicken and flip chicken to coat all sides.
Set Instant Pot to pressure cook on high for 20 minutes.
Meanwhile, in a small bowl, stir together the cornstarch and cold water; set aside.
When chicken is done cooking, allow the pressure to naturally release for 5 minutes, then do a manual release.
Remove chicken from instant pot and shred using two forks.
Set Instant Pot to saute. Stir the cornstarch mixture and add to Instant Pot. Once sauce gets to a boil, stir until slightly thickened.
Add chicken back to Instant Pot and stir to coat with sauce. Serve over rice and sprinkle with green onions. Enjoy!
Recipe by Simple, Sweet & Savory at https://www.simplesweetsavory.com/instant-pot-teriyaki-chicken/