When carbonated beverages are frozen, the water expands as it turns to ice, and the carbon dioxide gas gets squeezed out of the mixture as it solidifies. The pressure on the inner walls of the cans becomes a ticking time bomb.
source : http://weibo.com/2137665200/yz74T7z7r; http://gawker.com/5939212/viral-photo-of-scarred-child-serves-as-graphic-warning-against-putting-carbonated-beverages-in-the-freezer