If the sausage and bacon aren't already cooked, heat a bit of oil in a pair of frying pans over medium-high heat. In one, stir-fry the sausage until browned, then transfer to a large mixing bowl. In the other, cook the bacon until crispy, then set aside.
Cook the onion over medium heat until translucent, then add the garlic and stir-fry 1 minute. Add to the bowl with the sausage.
In a separate bowl, combine the eggs, milk, salt, and pepper. Stir into the sausage mixture along with the sweet potatoes. Pour into an 9x9" baking dish, sprinkle the bacon on top, and cover with foil.
Bake for 20 minutes, then remove the foil and bake an additional 15 minutes or until the eggs have set and the top has begun to brown. Serve garnished with green onions.