Mix soy sauce, vinegar, sugar, cornstarch, salt, and 2 tbsp water into a bowl sauce.
Heat oil in a wok, stir-fry peanuts until golden brown; remove.
In the same wok, sauté dry red chilies, ginger paste, and garlic paste for 1 minute.
Add diced capsicum squares and stir-fry on high flame for 2 minutes to keep crispy.
Pour in sauce mixture, stir until glossy and thickened, then toss with peanuts and serve hot.