Heat a large skillet over medium-high heat. Add the sausage and cook until brown and the fat is rendered, about 5 minutes. Add the onions and cook until soft, about 3 minutes. Add the garlic and cook 30 seconds. Remove from the heat and stir in the cilantro.
Over a hot grill or in a clean skillet over high heat, heat the tortillas until warmed through and pliable. Divide the sausage filling among the warm tortillas and serve with desired accompaniments.