Prepare the Vegetables: Shred or slice the cabbage and chop any additional vegetables like bell peppers or carrots. Slice the onion thinly and mince the garlic.
Heat the Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat.
Sauté Aromatics: Add the minced garlic and sliced onion to the pan. Stir-fry for 1-2 minutes until fragrant and the onion softens slightly.
Add Cabbage and Vegetables: Add the cabbage (and any other vegetables you're using) to the pan. Stir-fry for 5-7 minutes, stirring often, until the cabbage is wilted but still crisp.
Season the Stir Fry: Pour in the soy sauce, sesame oil, rice vinegar, and sugar. Stir well to combine all the flavors. Cook for an additional 1-2 minutes. Season with salt and pepper to taste.
Add Protein (Optional): If you're adding protein, such as tofu or chicken, toss it into the stir fry in the final step and cook until the protein is heated through.
Serve: Once everything is well combined and heated through, remove from heat and serve immediately.