Combine all of the ingredients except the radishes in a small saucepan and bring to a simmer, stirring occasionally until the sugar dissolves. Remove from the heat and let it cool for a few minutes while you prep the radishes.

Trim the leafy tops off and wash the radishes. Thinly slice and place in a pint jar.

When the brine has cooled a bit, pour it into the jar, making sure to cover the radishes completely. Allow to cool to room temperature, about 20 minutes. Seal the jar with a tightfitting lid and shake or rotate it to evenly distribute the brine and spices. The pickles will be ready in about an hour, but are best after a few hours. Store them in the refrigerator and they will keep for about a week.