McDonald's Filet-O-Fish is traditionally served with tartar sauce, but if you're looking for a way to switch things up, try swapping the tartar for any other McDonald's sauce.
For the most iconic McDonald's flavor, try swapping the tartar sauce with Big Mac sauce instead. Some Reddit users even order a Big Mac and sub the patties with fish fillets.
McDonald's also offers six dipping sauces, most of which would pair nicely with a fish fillet. For instance, you can use Buffalo sauce and ranch for a spicy ranch Filet-O-Fish.