I don't think co2 becomes dry ice once the water becomes ice. It stayed with the leftover water. Tidan' analysis makes a lot of sense. The leftover solution of co2 in water should have higher concentration of co2, lower melting temperature, and higher 蒸汽压.The upper limit of the pressure may be estimated through 2.2gram co2 trapped in the left over space of ice in a 415ml containter.

It would be interesting to see what happen if the temperature is just slightly below zero. If Tidan's reasoning is correct, which I believe is, only small amount of ice would form in concentrated Coke, and the container would not break.