First, Billy pickpocketed a Swiss Army Knife from a camping supply store. He used it to cut the tags off of the clothes he tried on in a children's store without being detected. He had always been small and talented at slipping through tiny spaces. Nobody even saw him come or go.
Next Billy went to the bathroom to clean the soot off of his face and arms. He couldn't look like he had been anywhere near fire. At this point he was about ready to collapse from exhaustion and dehydration but he pushed on and managed to make his way to the food court.
Somebody out there was looking out for him today; a twenty dollar bill was sitting out on a table for all the world to see. Well, it was his now! He stocked up on as much dollar menu food as he could from various places inside the food court.
He would have the perishable things like meat and the extra-large cup of soda first and save the bags of chips and water bottles for later. This might have to last him for a while.