Cut sausages, onions, bell peppers, carrots, and other vegetables into bite-sized pieces.
Heat cooking oil in a pan and stir-fry the sausages.
When the sausages are cooked, add the prepared vegetables and continue stir-frying.
Season with soy sauce, ketchup, pepper, etc., and stir-fry until well mixed.
When the vegetables and sausages are evenly cooked, turn off the heat and transfer to a plate.