So, I just opened up a bottle of lemon-flavored soda that had been sitting in my family's garage for a few years, and I noticed that its flavor seemed different than it normally is. I wasn't sure if it was safe to consume or not, so I tipped my glass out into the sink after a couple of sips, and then looked at the bottle and noticed that the color looked a little yellowish, rather than completely transparent like normal. One of my family members tried a small glass of it, noted that it lacked carbonation, and said it probably just tasted strange because it was flat.
The best before date on the bottle was in 2018, and we live in an area where temperatures in the summer can reach 30-40 degrees C, though I'm uncertain exactly how hot the garage gets. It wouldn't have been exposed to direct sunlight, though.
Can bottles of soda go off, either due to chemical changes in the soda, or due to the plastic in the bottle breaking down? It was sealed the entire time, so I don't think that any bacteria or wild yeast would have gotten into it, right?
It’s a regular soda, not diet. Ingredients on its label are “carbonated water, sugar, acidity regulator (330), natural flavour, preservatives (211, 202).”