I had that happen with some Heineken. Someone went with us on the last boat trip of the fall, and the cooler ended up sitting all winter and spring. I opened it up probably in May or June to clean it out, and here are all these green bottles floating in there. I iced them down, and they were actually far better than they come from the store. The caps were actually starting to rust a bit underneath too. I'm more of a dark sludge beer kinda guy.