Whisk the cornstarch and 1 tablespoon water together in a small bowl and set aside.

In a saucepan, combine soy sauce, 1/2 cup water, garlic, honey, and rice vinegar. Bring to a boil over medium-high heat, stirring continuously so the honey does not burn.

Once boiling, whisk in the cornstarch mixture and cook until thickened, about 1 minute. Remove from heat and let cool slightly.

Preheat the oven to 400°F and spray a baking dish with nonstick cooking spray.

Slice each chicken breast horizontally to create a pocket, leaving about 1/2 inch intact.

Place 2 pineapple rings inside each chicken breast and arrange them in the baking dish.

Season with salt and pepper, then generously brush with the teriyaki sauce.

Bake for 20 minutes. Switch the oven to broil and broil for 3–4 minutes until lightly caramelized on top.

Serve immediately.