Heat a large skillet over medium heat and stir in the sausage and garlic. Cook and stir for 5 minutes, then add the onion. Continue cooking and stirring until the sausage is crumbly, evenly browned, and no longer pink. Drain and discard any excess grease. Combine the sausage with the eggs, tomato, cilantro, jalapeno, and taco seasoning. Allow mixture to cool to room temperature, then stir in the Cheddar cheese.