Steps
1. In a bowl, combine brewed coffee, soy sauce, brown sugar, and minced garlic to create the marinade.
2. Add beef strips to the marinade and let sit for 15 minutes.
3. Heat olive oil in a pan over medium-high heat.
4. Remove beef from marinade (reserve marinade) and stir fry beef strips until browned, about 3-4 minutes.
5. Add sliced bell pepper and onion; cook until vegetables are tender-crisp, about 3 minutes.
6. Pour reserved marinade into the pan and cook for an additional 1-2 minutes to thicken slightly.
7. Season with salt and pepper to taste.
8. Serve hot, optionally over cooked rice.