I am not sure of the proportions so PLEASE be careful, but if it has to have the pop in the bottle you mix baking soda in with it and the foam will create air pressure. Or you can use baking soda and vinegar, whatever you use you put them in shake a bit, and put down by the car. If it is a full bottle of soda just keep shaking it, then lay it on its side. This will create air pressure when you open it. Hope this helps
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