TIL that in 2020, Burger King ran an advertising campaign featuring a picture of a moldy Whopper, to prove that their burgers are made without preservatives. This unconventional advertising method worked, increasing sales by 14% (according to multiple sources.)
And 5 years earlier Burger King sold a burger with so many synthetic dyes that it turned people’s poop neon green.
https://www.usatoday.com/story/news/nation-now/2015/10/08/why-black-whopper-turns-your-poop-green/73623596/
Tasted alright though from what I remember