Step 1

Combine vinegar, water, sugar, mustard seeds, and salt in a small saucepan. Bring to a boil over high, and boil, stirring constantly, until sugar dissolves, about 1 minute.

Step 2

Place cabbage, carrots and radishes in a medium bowl. Pour vinegar mixture over slaw mixture, and stir to combine. Chill, uncovered, 12 minutes. Drain and serve.