In a large skillet, heat one tablespoon of the vegetable oil over medium heat. Add the onions, peppers, and jalapeno, sprinkle over the sugar, season with salt and pepper, and sauté for about 8 to 10 minutes until fairly tender. Transfer to a plate, and carefully wipe out the hot skillet.
Return the skillet to medium high heat, add the sausages to the skillet, and cook, turning them somewhat frequently, for about 10 minutes until lightly browned and cooked through. Cut them into pieces that will comfortably fit into the buns.
Pile the pepper and onions and sausage in the buns. Cut in half if desired, and serve.