The 'work' is done, I think it is obvious, by the liquid. If the guy was really interested in the behaviour of the gas, he would have had to use a pressurised bottle with only gas in it; but now he gives the impression, perhaps deliberately, that the soft drink is the liquid fuel... The 'experiment' is complete nonsense, with or without string.
With his HD camera, perhaps he should have been watching the atmospheric pressure sensor to document minutely the change in air pressure - of course, that would probably require an 'HD sensor' too, I don't know if such a thing exists. Anyway, if you want to know something, you have to do hundreds and thousands of experiments, not just one.
Videos of this type are run under the prestigious heading of 'experiment', but should be called a demonstration, not in the regular meaning (demonstrating a known fact with an 'experiment'), but in a purely propaganda sense. On the basis of 'a picture is worth a thousand words'.
Among other videos of the author gentleman, one shows a balloon and another a mini drone, also in a vacuum chamber. The behaviour of both objects as shown in the two videos respectively, under zero atmospheric pressure, is utter nonsense, so the two psychological categories above could perhaps be brought together under a common heading: a liar. For the 'idiot', unless it is a medical case, I can offer no excuse - he himself made an idiot of himself. (I would rather withdraw my previous indulgence of them.)
As for the 'infinite vacuum': many people raise the idea that if there were a vacuum, the atmosphere could not exist. So when the air runs out, something has to remain. The question is what that is. I guess there is no empirical answer to that. Not just 'not yet', but not at all.
To return: trying to produce experimental conditions, simulations, of which we know nothing about the original seems to be an interesting effort.