They may be empty, but they'll be closed up, surely. I don't think sound waves will get them to reverberate. You'd probably have to step up to one and hit it with a stud (2 by 4) or baseball bat to get it to make a sound.

In other words, a blunt instrument rather than an instrument.

I give the musos two hours before somebody wonders how to incorporate a container as a percussion instrument, however.