Both opened and unopened canned soda can go bad, but the exact time frame differs depending on type and storage conditions. On average, canned sodas using natural sweeteners should be used within nine months of production.
Nine months after production, properly stored canned soda is still safe to consume, but the carbonation and taste may be affected. Diet canned sodas have a shelf life of three to four months due to the use of artificial sweeteners. The same shelf life applies to sodas that are packaged in plastic bottles. Improper storage of canned soda can also reduce its shelf life.