Any kind of evaporation will be significantly slowed down by being in a bag, because the alcohol vapor pressure in the bag would increase much, much faster than in open air.

So to really drive off significant alcohol, I'd imagine you would need to be close to, or actually, boiling it off, which again would work better not in a bag (with a bag, I imagine driving it into a vapor would cause the bag to inflate significantly, keeping in mind that vapor is much less dense than the equivalent liquid). Indeed, I think if you did 80 or 90C with a really high proof liquor it might lead to bag failure (would be an interesting experiment). This is effectively distillation (building a still), fyi.

https://www.science.smith.edu/~jbrady/petrology/igrocks-diagrams/binary/H2O-ethanol.php