Hamburger Sauce (Like In and Out)

I love good grilled hamburger, and the secret is their sauce:

here is the copy cat version of in and out burger from chef in training, you can see the picture here:

1/2 cup mayonnaise
2 Tblsp ketchup
1 Tblsp white vinegar
2 tsp sugar
2 tsp sweet pickle relish
2 tsp finely minced onion

dash of salt and pepper

Mix ingredients together in bowl, cover and let set in fridge

How to put together a hamburger:

bottom bun, spread with special sauce, tomato slices, iceberg lettuce, add hamburger with melted cheese, then slices of onion, top with top bun that was spread with special sauce as well.