It bothers John A Lot that Billy's trying to be the bigger man, being reasonable with him despite numerous attempts at poking the bear. Makes John look bad. It's not like he really wants to fight. He's tired. He just can't let his guard down because he knows that's exactly when someone's going to take advantage of him. He has a better chance going at this alone than some masochistic fuckwit with a soft spot for a potential runaway.

John's getting ready to snap at Billy for being a piece of chewing gum stuck to his shoe when he brings up 'better meal' and 'drink'. He stops abruptly and turns, eyes widening a little. John instinctively is more willing to trust someone who can't be that much older than him than someone twice his age luring him into the back of some pedovan.

Plus, if Billy is able to get him a drink...

"...what's there to eat around here?"