Answer: Cash
He runs over to April and hands her something, surprising her. She says, "What's this?" Danny answers, "It's something I owe you. Trust me." She opens her hand for the camera and we see that it is a $20 bill.
Earlier in the movie, Danny and his father stop by April's house to make sure she is okay after her mugging. While George (Danny's father) and April are talking, Danny is sitting alone at the table and notices April's wallet. He opens it and steals some money from her.