It seems like a simple question, but I find it quite worrying. My cousin had a 2 litre bottle of coke which he opened and kept in his room, only drinking a glass or 2 out of it, and then he put it in his cupboard and forgot about it. About a month later he was in bed one night and woke feeling really thirsty. He was too tired to plod down the stairs to the kitchen for a glass of water, (he was also half asleep) but remembering the bottle of coke (even though he knew it had been opened for so long), he took a long drink of it and went back to sleep. He told me about it a few days later and said that it had tasted horrible and he'd thrown the rest away. He is now worried that perhaps because it was left for so long and had gotten really flat, and the air had got into it, that perhaps some of the chemicals in it might have damaged him in some way. Hes not a kid, hes 26, and I can see his point. Could some of the chemicals in it have become dangerous because of the length of time it had been opened? Advice please?