1 medium English cucumber
1/4 cup seasoned rice vinegar
1/4 cup water
3 tablespoons sugar
1/2 teaspoon salt
Halve cucumber lengthwise, then slice crosswise 3/4 inch thick.
Bring vinegar, water, sugar, and salt to a boil in a saucepan, then cool to room temperature.
Combine cucumber, radish, and vinegar in a bowl and chill, covered, until cold.
Drain vegetables before serving.