Wash and trim both ends of the watermelon radishes. Cut the radishes into thin rounds or your desired shape. Place in a heatproof jar or bowl with the bay leaf and peppercorns.
Heat vinegar, water, sugar, and salt in a small pan until the mixture comes to a boil and the salt and sugar are dissolved.
Pour the mixture over the radishes, Push the radishes down until completely submerged. Add more water if needed.
Allow the watermelon radishes to rest in the fridge for 20 minutes. Pickles will keep up to a week in the fridge.
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Notes
The pickling spices can be adjusted to your tastes. Try fresh herbs or dried chili peppers.
Apple cider vinegar or white wine vinegar can be substituted for the white vinegar.