Place the mayonnaise, yogurt, relish, capers, herbs, sugar, and vinegar in medium sized bowl and whisk to combine.
½ cup mayonnaise, ½ cup plain Greek yogurt, 2 tbsp dill relish, 2 tbsp capers, 1 tbsp fresh dill, 1 tbsp fresh parsley, 1 tsp granulated sugar, 1 tsp white vinegar