In a small bowl, whisk together mayonnaise, ketchup, vinegar or lemon juice, sweet pickle relish, and onion powder until smooth.
Season with salt and pepper. Add sugar, Worcestershire, or hot sauce if using and mix to combine.
If the dressing is too thick, add a teaspoon of water or milk to reach your preferred consistency.
Fold in chopped hard-boiled egg if using.
Cover and refrigerate at least 30 minutes before serving.
Serve over salads, as a burger sauce, or as a dip for vegetables, fries, or onion rings.
