Place the 4 boneless, skinless chicken breasts in the Instant Pot in a single layer.
In a mixing bowl, whisk together 1/2 cup ketchup, 1/4 cup sriracha, 1/4 cup honey, 2 tablespoons soy sauce, and 1/2 cup water until smooth.
Pour the sauce mixture evenly over the chicken in the Instant Pot.
Close the lid, set the valve to sealing, and cook on high pressure for 10 minutes.
When cooking finishes, perform a quick pressure release according to your cooker’s instructions, then open the lid and transfer the chicken to a cutting board.
Turn the Instant Pot to Sauté. In a small bowl, whisk 3 teaspoons cornstarch with 1/4 cup cold water to make a slurry.
Stir the cornstarch slurry into the hot sauce in the Instant Pot and simmer for a few minutes, stirring, until the sauce thickens.
While the sauce thickens, cut the chicken into bite-size pieces and return it to the pot. Stir to coat with the sauce and heat through for 1–2 minutes.
Serve the honey sriracha chicken over cooked rice and garnish with chopped scallions to taste.