Because of the carbonation and carbon dioxide in soda, it doesn't ever completely freeze, but it can turn into a slushy semi-frozen mixture in approximately three hours. Diet sodas respond a bit differently.
While water freezes at 32 degrees Fahrenheit, the carbon dioxide in soda causes it to freeze at the slightly lower temperature of 30 degrees Fahrenheit. Even if a soda bottle is left in the freezer or outside in freezing temperatures, the liquid inside will retain its liquid status. When the bottle is opened, the release of the carbon dioxide instantly forms small ice crystals, creating soda slush. Not all soda containers can withstand three hours of freezing, however; aluminum cans have a tendency to explode before that time, showering the inside of the freezer with the soda slush.