Soak the sweet potato noodles in warm water for about 30 minutes or until soft.
Drain the noodles and set them aside.
Heat vegetable oil in a large pan or wok over medium heat.
Add the minced garlic and sauté until fragrant.
Add the beef (or tofu) and cook until browned.
Stir in the onion and carrots, cooking for 3-4 minutes until softened.
Add the bell pepper and spinach, cooking until the spinach wilts.
Add the drained noodles to the pan.
Pour in soy sauce, sesame oil, and sugar, tossing everything together.
Garnish with sesame seeds and green onions before serving.