Wash the radishes and trim the ends. Slice into quarters and put in a ceramic or glass (non reactive) bowl. Sprinkle with the salt, rub it in a bit, and let sit for 5 minutes or so. You will see some moisture, "sweat".  Toss, press and squeeze the radishes to get rid of excess moisture, then rinse under running water to remove the excess salt. Squeeze dry again and put back in the bowl.

Mix the sweet and sour sauce together and pour over the vegetables. In just half an hour, you'll have a nice lightly pickled radish.