Potassium Metabisulfite
If you have it, it sounds like it’s a better option than whatever easy ethanol source you’ve got. But the trick to proper sterilization is that certain microbes are resistant to different things. The Potassium Metabisulfite sounds like it’s about as nasty, but less toxic, than bleach. However even that alone isn’t enough for sterility.
Glassware is usually fine so long as you allow pressure to build and release slowly.
For what you’re doing there are additional microorganisms which can outcompete anything you don’t kill and so “sterile enough” is probably fine, but putting this here as something to keep in mind in case things go wrong.