Coat grill rack with nonstick cooking spray and preheat to medium heat (300-350°F).

Cut tofu into 1/2-inch thick slices and place in a single layer in a shallow dish.

In a small bowl, combine teriyaki sauce, honey, sesame oil, minced garlic, grated ginger, salt, and pepper.

Pour the teriyaki mixture over the tofu, cover with plastic wrap, and refrigerate for at least 30 minutes to marinate.

Remove tofu from marinade and transfer leftover marinade to a saucepan.

Boil marinade over high heat until reduced and slightly thickened.

Reduce heat to very low and start grilling the tofu.

Grill tofu for 5-6 minutes per side, turning gently, until lightly charred and heated through.

Remove tofu from grill and drizzle with reduced marinade.

Sprinkle with thinly sliced green onions and red pepper flakes (optional).

Serve immediately.