In a large bowl, combine tamari, apple cider vinegar, sriracha, Chinese five-spice powder, brown sugar, garlic, sesame oil, and whites of scallions. Transfer 2 tablespoons of sauce to a small bowl and set aside.
Add wings to sauce in large bowl and toss. Refrigerate covered at least 1 hour or up to overnight.
Add water to the Instant Pot® and insert steamer basket. Place chicken wings in basket, arranging them so they aren’t sitting on top of one another; place them standing up if necessary. Lock lid.
Press the Manual or Pressure Cook button and adjust cook time to 10 minutes. When timer beeps, let pressure release naturally for 5 minutes. Quick-release any additional pressure until float valve drops and then unlock lid.
Using a slotted spoon, transfer wings to a baking sheet. Brush with 2 tablespoons of reserved sauce. Broil wings 3 minutes on each side to crisp the chicken.
Transfer wings to a serving dish and garnish with sesame seeds and greens of scallions.