Whisk together the buttermilk, mayonnaise, and sour cream in a bowl.
Stir in the garlic powder, onion powder, sugar, chives, dill, parsley, salt, and pepper.
Cover and refrigerate at least 1 hour up to 24 hours before serving. Taste and adjust spices if necessary. If it gets to thick, thin it out with cold water 1 teaspoon at a time.