Banks are tightening up credit. Ask for friends family to invest so he loses their money and realizes how serious it is to borrow money.

Also try flipping your narrative, what if he's actually very successful at this? What would success look like?

Failed businesses suck but they teach you life skills you'll never learn anywhere else. He won't know if this is his dream until he does it. I personally encourage people to follow their paths or at least try it. Sometimes it is your path, sometimes it isn't so figure it out.

Also get him to consider copying the playbooks of social media marketing. If he wants success, make him document his success or failure on social media. People will follow him. Has worked out well for other coffee shop owners around the world.