Heat oil in a skillet over medium heat. Add onion and garlic; cook and stir until onion has softened and turned translucent, about 5 minutes. Stir in sausage; cook and stir until sausage is crisp. Stir in water, rice, tomato sauce, adobo seasoning, salt, and black pepper; bring to a boil, then reduce heat to low. Simmer until rice is tender and liquid has been absorbed, about 20 minutes.