Easiest way, change your BTC for cash and give that to him. Certainly in the current climate no one is going to want to accept bitcoin for goods.
They're not accepting Bitcoin if they use a payment processor. They're receiving dollars sent using BTC as a payment rail. In quite a few places people would rather stay away from banks and let a payment processor handle the conversion. Less potential for the bank getting arsey.
Most shops will just change it to fiat straight away.