In a large bowl, add sliced cucumbers, green onion, and sweet onion. Stir to combine.
In a small bowl, whisk together extra virgin olive oil, sugar, Catalina dressing, white vinegar, salt, and pepper. Pour the dressing over the vegetables and stir well to coat.
Refrigerate for at least 15 minutes before serving to allow flavors to meld.
Notes
This cucumber salad is best served chilled. It's a perfect side dish for picnics, BBQs, and summer meals.