Expired milk tastes pretty fucking foul, as do most other rotten things. Mouldy bread is also quite gross, although not really on the same level.
Other than that, the most disgusting thing I can remember is my cough syrup from when I was younger. It was supposed to taste like cherry or something, but it tasted like chemicals and was sickeningly sweet.
Other than that, the most disgusting thing I can remember is my cough syrup from when I was younger. It was supposed to taste like cherry or something, but it tasted like chemicals and was sickeningly sweet.