If the soda is frozen in a plastic bottle, it can just be set out to thaw; however, proceed with caution if it is in a metal can or glass bottle as it could explode. To defrost a plastic bottle, simply removethe bottle from the freezer and set it out at room temperature or in the refrigerator.
The main concern when dealing with frozen soda is the risk of explosion. Liquids naturally expand when they freeze. Even a bottle of plain water will stretch its plastic container when frozen. If it is glass or metal, it can rupture the container, causing an explosion. Most likely this will occur inside the freezer, causing only a mess, rather than an injury.
However, dealing with soda introduces the increased risks related to carbonation. Soda is made of water mixed with solutes, including flavorings and carbon dioxide bubbles. These solutes lower the freezing point of soda below what plain water would be. Therefore, a soda left in the freezer may still be slushy for awhile. However, when the container is opened, the carbon dioxide gas is forced out rapidly, and in the absence if this solute the freezing point of the remaining liquids goes up, meaning that the soda may freeze instantly.
This freeze causes an almost instantaneous expansion of the container. If the container is plastic, it will probably just swell. However, if the soda is in a glass bottle or aluminum can, the container may explode.