I am given to understand there is some dispute about whether Ketchup is an allowable condiment for Hot Dogs.
No more or less than it is on Hamburgers.
At Louis’ Lunch in New Haven, home of the original Hamburger, a Burger “with the Works” is a slice of yellow American Cheese, a slice of Tomato which is nice when in season, and a slice of Onion which is more or less hot depending on season. Feel free to mix and match. There might be Salt and Pepper floating around, I misremember. It is very small and crowded.
Did I mention it’s served on dry toast?
Yes, smuggling in packets you stole from other Burger joints makes you weak and worthless.
Me personally? Depends on the Bun. Ketchup and Brown Mustard always. I’m not above adding Cheese, Kraut and Chopped Onion or even Chili (though I have to be careful because of my allergies) to my Dogs. Bacon, Cheese, and Sliced Onion to my Burgers and if the Tomatoes are nice they add but mostly they turn into slippery goo that slides your Slider (Hah!) all over the place.