Bandwidth doesn't help much with bitcoin mining, I have a few questions for your friend.

There's not some program you can "donate" bandwidth to and make money off of it. Closest thing would be to self-host media and stop paying for all the streaming services you probably have right now. That will save you money, at least.

There is one:

https://pkt.cash/

from the maker of https://github.com/cjdelisle/cjdns

And there is https://sia.tech/ (Network too but mostly about storage)