I drink about two diet cokes a day and love the product. However, sometimes when I purchased bottled diet coke from places like gas stations it has mildew or moldy smell to it. I just purchased a bottle from BP in Florence, KY, off Burlington Pike and it smells so bad I have to dump it out. What is causing this smell? Why does it only happen every once in a while? Again, I love diet coke, but I am concerned about the smell and what could be contributing to it.