I got this recipe from the Kind Diet cookbook by Alicia Silverstone.
6 radishes, sliced thinly
3/4 c. Ume Plum Vinegar
1 1/2 c. water
Put radishes, vinegar, and water into a glass jar. Cover with cheese cloth and let sit for 24 hours to 3 days. Rinse radish slices in cold water and discard the vinegar and water mixture. Keep the radishes for up to ten days in the glass jar, then refrigerate. I just put mine in the fridge right after I rinse them because I think they taste better cold and crispy. These radishes will help your digestive health, so eat up!