I'm not 9 years old, and I like ketchup. I like it on hamburgers, hot dogs, meatloaf, and french fries. For decades Heinz was the gold standard of ketchup. My FIL, who worked for S&W foods secretly used Heinz ketchup at home. Then, some while back, Heinz made a deal with the devil and substituted high fructose corn syrup for the sugar. So I dropped Heinz like the dirt that it became. Sampled quite a few and have settled on Annie's. It's organic and uses no HFCS. Heinz realized their grievous error and brought back New Heinz, with sugar and no HFCS. But they lost me as a ketchup customer.
Now, a word about mustard. Yes, I use cheap yellow mustard on my Costco hot dog because that's all they offer. I used that yellow junk much of my life cuz that's what my mom had at our house. I'll make my usual pitch. Then on a Grand Ronde float trip in 1985, we were roasting Asotin County chicken (chukar) on the fire, and one of my camp mates introduced to to Plochman's mustard. It's stone ground and has a bit of horse radish in it. We slathered those chickens in Plochman's, and it has been my go to ever since. The local grocery stores stopped carrying it over 10 years ago, so I order it by the case online. All other mustard fails by comparison, except one by Boar's Head that is almost exactly the same and carries the Boar's Head price mark up.
At first I thought it was sad that Costco dropped the Polish sausage from the food court menu. But then I realized that the all beef hot dogs don't adversely affect my stomach the way the Polish sausages did. Like that old age syndrom Mossback mentioned about onions. Raw onions don't agree with my stomach generally, so I really favor sauteed or caramelized onions - get the flavor without the negative acid affect.