>Surely they could (will?) be charged with something though, right? I mean if I walk down the street now and launch a sandwich at a random stranger, it's some form of assault. "Attempt to cause bodily injury" is a bit much, but it's something.

Littering?

Another, similar case[0] was also brought, in Massachusetts some time ago. And there were, at least temporarily, some negative impacts on the defendant[1].

[0] https://youtu.be/zPx2t7xoF1k?t=390

[1] https://youtu.be/zPx2t7xoF1k?t=657