Supercooled Liquids
by djlosch

The dissolved particles in water lower the freezing point. (This is why you put salt on ice during the winter to melt the ice.) When you open the bottle, the concentration of dissolved CO2 changes because the bottle has been opened/depressurized. The loss of pressure causes CO2 that has been forced into to solution to escape from the solution (usually forming bubbles along the side of the glass), lowering the concentration and raising the freezing point. The temperature now being less than the freezing point and the water freezes.

As noted vibration can also knock dissolved gasses out of solution causing the water to freeze although it usually takes a more dramatic loss of concentration to really freeze the drink.