In a large bowl, toss the cucumber slices, sugar, and salt. In a small bowl combine the onions, jalapeños and vinegar, toss to combine. Let stand for 10 minutes at room temperature.
Add the vinegar, onions, jalapeños, radishes, and chopped dill, to the cucumbers, then gently toss to combine.
Cover and refrigerate for at least 30 minutes, before serving.
Prior to serving, pour the excess liquid into a small bowl or jug and serve on the side.
Arrange the salad on a platter (or serve directly from the bowl), garnish with dill leaves and enjoy!