Carbonated drinks are safe to consume almost indefinitely beyond their expiration dates. However with time, the sweeteners in the beverage break down and the taste of the drink is altered.
Any food item labelled with an expiration or sell-by date is usually safe to consume after that date has passed. This is because most expiration dates are used as a point of reference for grocers to know what date to sell a product by. It is after that date that the item begins to deteriorate, though it might be safe to eat for days or even weeks after it has "expired." Each food is different.
Carbonated Drink Shelf Life
Soda has a longer shelf life than its expiration date would suggest. Diet soft drinks will last three to four months after their sell-by date before the artificial sweeteners break down and alter its taste. Regular soft drinks (that contain sugar and not artificial sweeteners) will last six to nine months past their sell-by date.
To maximise a soda's shelf life, store cans and bottles in a cool, dry place. Clear plastic soda bottles should be kept out of sunlight, as the light will cause the sugars to break down faster.
glass of soda image by Kalani from Fotolia.com
Because carbonated drinks are comprised mostly of water, sugar and artificial flavours, they never really go bad. If the sugars in the beverage break down, the taste will be different, but it will still be safe to drink.