Wash daikon and carrots and cut into matchstick sizes, or round sizes (about thickness of a 25¢ quarter). Pat dry. In bowl, mix vinegar, salt, sugar and water until the sugar dissolves. Add the carrots and daikon to the mixture and let marinate for at least 1 hour before serving. For best pickled flavor, store vegetables in an airtight mason jar for about 5 days in the refrigerator.