How do I clean the inside of old, antique glass bottles?

We are digging up the ground to bury a septic tank and found a whole stash of old, glass bottles that I would like to clean up and possibly display. The outside of the bottles wasn’t too difficult, but I can’t fit anything (like a toothbrush) down into the openings on most of the bottles. Is there some way to clean these without scrubbing? I thought about the dishwasher, but kind of hate to have all this dirt and grime in there. Denture cleanser maybe????