Shot for the advice! I have been digging a bit on the interwebs, and there is quite a few opinions on this. What seems credible to me:
Polyester houses various funky bacteria better than cotton, hence the odour build-up is because the microscopic swarm! eek!
Other problems are mildew and fungi.
In terms of solutions:
Vinegar has been mentioned mostly in relation to mildew.
Bleach could be a good all-round solution but risky to colors.
Soaking in an anti-bacterial solution is mostly recommended for odour.
Some lady swears by a certain essential oil, but then sh also sells it on her website…mmmmmmmm
I’ll give a dettol-solution soak a bash and report back.