Whisk together soy sauce, cornstarch, rice vinegar, ketchup, brown sugar, and water. Set aside.
Heat coconut oil in a large skillet over medium-high heat. Add tempeh, green pepper, pineapple, and garlic. Cook until just beginning to brown, 5–7 minutes.
Whisk sauce again and add to skillet. Cook until sauce is thickened, 1–2 minutes more, then remove from heat. Serve over rice.
Notes
I like my sauce more sweet than sour, but if you're the opposite, start with one tablespoon of brown sugar and add more, one teaspoon at a time.
Craving more veg-friendly recipes? Shop our collection of vegetarian and vegan cookbooks, including our new Vegan Thanksgiving and Vegan Christmas cookbooks!