Combine sweet potatoes, onion and taco seasoning in large nonstick skillet over medium heat. Add water. Cover and cook 8 to 10 minutes or until crisp-tender and water has almost evaporated, stirring once.
Stir in oil; continue cooking, uncovered, 4 to 6 minutes or until potatoes are tender and begin to brown, stirring occasionally.
Add beef to potato mixture. Continue to cook 5 minutes or until beef is heated through, stirring occasionally, adding 1 to 2 tablespoons water, if needed to avoid sticking.
Serve in tortillas and garnish with sour cream, hot pepper sauce, and cilantro, as desired.
If you don’t have any cooked beef just cook some up. I used a sirloin and cut it into cubes. Then seasoned it and cooked it in a skillet.