In a medium mixing bowl, mix sugar, vinegar, water, and salt. Stir until the sugar and salt are dissolved. Now you need to taste; if it’s too tart, add more sugar, 1 tablespoon at a time till you reach the point where it’s neither too sweet nor too sour, but a balance of the two. Same goes for the vinegar - if you want it more tart, add more vinegar. If it's too strong, add more water. Set aside.
In a large serving bowl combine the cucumbers, onions, and dill. Pour the sugar-vinegar liquid over cucumbers and onions, letting them sit in the refrigerator for 4 or more hours. The longer it sits, the better it will taste! I would turn the salad once to make sure every bit of cucumbers gets coated. Serve at room temperature, or chilled.