Place the Brussels sprouts in a large mixing bowl. Add the olive oil, onion powder, 1/2 teaspoon salt and 1/4 teaspoon pepper and toss to thoroughly coat. Pour the sprouts into the basket of the air fryer and spread out in an even, thin layer. Cook, tossing halfway through, until crispy with tender cores, about 12 minutes.
Combine the teriyaki sauce, ginger, rice wine vinegar and garlic in a small bowl and stir to combine. Serve with the warm Brussels sprouts.
If you prefer halved sprouts, increase the cook time by 5 to 8 minutes. The larger the air fryer (or the more spread out the sprouts), the shorter the cook time.