worst foods for challenging non-stick frying pans?

What foods have you encountered that in your humble opinion laugh at any supposedly “non-stick” frying pan? The two worst I know of are Spam, and Morningstar Farms Veggie Sausage Links. Both are processed concoctions that are held together by essentially food grade glue, and it shows.

I was going to say veggie sausages too, but the real deal - sweet Italian sausage - is the big winner in my kitchen.

Fudge, if you let the remnants dry inside the container.

My first reaction would be an egg - not scrambled, no oil in the pan.

But the only thing I’ve ever seem stick really stubbornly was cheeseburgers.
If you get the pan good and hot without oil and drop in the burger you’ll get a nice crust on it - top that with a boatload of cheese and the combination of the crusty burger leavings and the cheese seems to be a pretty impervious and stubborn barrier.

any fish you want to pan-fry with some oil (assuming you don’t know how.)

Good question. I don’t own any non-stick skillets or sauce pans or saute pans now, but I like my pans for steak, sausages, to be good and hot before introducing the meat (wow, that sounds vaguely sexualized). I never had a non-stick I could let get very hot empty without damaging it.