Can you use glass cups instead of jars? For mushies

?

With pressure cooker?

Yes, just use a couple layers of foil as the lid

I did see someone do it on YouTube so sure probably not the most ideal way but if you are too cheap to buy jars.

I wonder. Is the Op really just trolling around? Or is he really just that...

Use any container that fits the parameters. You can seal it and it withstands 250 degrees for an hour or so.