Heat the oil in a frying pan, add the sausages and fry for about 10 minutes, turning frequently, until browned. Transfer to a plate.
Add the onions and sugar to the pan and cook gently, stirring frequently, until lightly browned. Return the sausages to the pan with the sweet potatoes, sage leaves and a little salt and pepper.
Cover the pan with a lid or foil and cook over a very gentle heat for about 25 minutes, or until the potatoes are tender and the sausages are cooked through. Drizzle with the vinegar and adjust the seasoning if necessary, before serving.
Recipe courtesy of The Hungry Camper Cookbook, by The Hungry Cookbooks, published by Octopus Publishing. Available at good book stores for R180