Slice the cucumbers and red onion thinly, then place them into a large serving bowl.
In a smaller mixing bowl, whisk together the sour cream, mayonnaise, white vinegar, chopped fresh herbs, garlic powder, salt, and black pepper until completely smooth.
Pour the dressing over the sliced vegetables and toss gently to ensure everything is evenly coated.
Cover the bowl and chill in the refrigerator for at least 30 minutes to allow the flavors to blend before serving.