What should I do with all my empty glass vases?

https://www.hometalk.com/search/posts?filter=glass%20vases

If you don't need all of them, maybe you could donate them to a local non-profit. There's an organization in my area that takes donated wedding flowers & breaks them down into several smaller bouquets , using donated flower vases. They then donate the flower bouquets to local nursing homes to brighten up the elderlys' days.

Donate to thrift store

I use a few for rooting cuttings. I have one at work with philodendron in it. If you have any young people starting out with their first apartment, offer a few. I keep a few on hand to give away. I give flowers sometimes to others, and take them I a vase. That way I have no need to get it back. Tell them to keep it or pass it on.

I donated mine to a local florist. They were very happy to get them.