In a bowl, whisk together the soy sauce, honey, rice vinegar, sesame oil, garlic, ginger, and 1/4 cup water until well combined.
Place the chicken thighs in the Instant Pot and pour the teriyaki sauce over the top. Lock the lid, set the valve to sealing, and cook on high pressure for 10 minutes.
When the cook time is done, let the pressure release naturally for 5 minutes, then carefully turn the valve to venting to release any remaining pressure. Transfer the chicken to a cutting board.
Set the Instant Pot to saute mode. In a small bowl, whisk together the cornstarch and 2 tablespoons of water until smooth. Pour the slurry into the sauce in the pot and stir continuously for 2 to 3 minutes until the sauce thickens and becomes glossy.
Slice or shred the chicken and return it to the pot. Toss to coat everything in the thickened teriyaki sauce. Press cancel to turn off the heat.
Serve the teriyaki chicken over cooked white rice and garnish with sesame seeds and sliced green onions.