Cut the sausages open at one end and squeeze out the sausage meat into medium-sized meatballs. (I got 3 meatballs from each sausage).
Form the meatballs with damp hands then fry in a hot frying pan with 2 tablespoons olive oil. Cook until golden brown then remove from the pan.
Add the onion and garlic and cook until soft and fragrant then add the chopped tomatoes, thyme, vinegar and sugar.
Cook for 5 minutes then add the meatballs back in and cook for a further 5-10 minutes until the meatballs are cooked through and the sauce has reduced slightly. (If the sauce seems too thick to begin with, add a splash of water).