Place your sweet potato into a microwaveable bowl. Cover. Microwave for about 3-4 minutes on high - until potatoes are cooked but firm.
In medium bowl, combine cider, soy sauce, cider vinegar, garlic, onion, salt and pepper. Add steak tips. Marinade for at least 30 minutes (ideally 3-4 hours in the fridge).
Skewer your steak, sweet potatoes and onion on your bamboo skewers.
Grill on medium high for about 10-12 minutes, turning once during cooking.
Serve warm.
