depends on what I can find in my fridge. I might put Ketchup, mustard, mayo, hot sauce, liquid cheese, shredded cheese, chili, ground beef, baked beans, lentils, sauerkraut, caramelized onions, relish, bacon, bell peppers, avocado, salsa, teriyaki sauce, grilled onions, butter (a bit slathered on the hotdog bun), or coleslaw.
Things I wouldn't add to it, but other people do: Pickles, grilled corn, diced tomatoes, diced carrots, jalapeños, cucumbers.
If you're using a quality sausage, they can taste good plain as well.
Massive warning: Do not add all of this at the same time, just 1 or 2 sauces and 1 topping.
