Chicken, tomato & cucumber salad

Chicken second courses

5 tablespoons olive oil, divided 1 pounds chicken breast tenders Salt and ground black pepper ¼ cup cider vinegar or white wine vinegar 1 tablespoon snipped fresh thyme 1 teaspoon sugar 1 medium cucumber, cut in thin ribbons 2 tomatoes, sliced ½ cup pitted green olives, halved and/or sliced 4 ounces feta cheese (optional)