Note: If you're using wooden skewers, soak them in warm water for 30 minutes beforehand, so they don't burn on the grill.Heat a grill pan or outdoor grill to medium (about 350°F). Meanwhile, alternately thread 4 peach quarters and 4 sage leaves on each skewer. Season well with salt and pepper.Rub the grill with a towel dipped in oil and place the skewers and sausages on the grill. Cook, uncovered and turning occasionally, until the peaches are charred and soft and the sausages are cooked through, about 20 to 30 minutes.Remove from the grill, drizzle cider vinegar over the peaches, and serve immediately.