Combine beef sirloin pieces with Coca Cola, soy sauce, garlic powder, and black pepper in a bowl.
Marinate in the fridge for at least one hour.
This allows the flavors to penetrate the meat, making it tender and flavorful.
Heat olive oil in a large skillet over medium heat.
Add onion, green bell pepper, and red bell pepper.
Sauté until they are soft and onions are translucent.
Remove the marinated beef from the fridge and drain it, discarding the marinade.
Add the beef to the skillet with the sautéed vegetables.
Cook the beef, stirring often until fully cooked, about 7-10 minutes.
Reduce heat to low and ensure the beef and veggies are well combined.
Cover the skillet and let the mixture simmer for an additional 5 minutes.
This helps meld the savory flavors together beautifully.
Serve these steak tips hot alongside your choice of sides.
They're fantastic with mashed potatoes or steamed vegetables.