Press tofu to remove moisture, then cut into cubes.
Toss tofu with cornstarch for crisp edges.
Heat vegetable oil in wok over medium-high heat.
Add tofu and stir-fry until golden brown, about 6 minutes.
Remove tofu and set aside.
In the same pan, add sesame oil, garlic, and ginger; stir for 30 seconds.
Add bell peppers and cook 2–3 minutes until slightly tender.
Whisk soy sauce, rice vinegar, maple syrup, and water in a bowl.
Pour sauce into wok and stir until it thickens slightly.
Add tofu back, toss well, and sprinkle sesame seeds before serving.