Initially to reward the boys for whatever the reason (sleeping by themselves, eating their entire meal by themselves without having to be constantly reminded, brotherly help, sharing toys, no whining for the entire day, etc.) I used reward calendars
from Chuck E Cheese. If they did any of the previously mentioned good deed, then they would get a sticker to put on an empty day and once they completed their calendar, their reward was a trip to Chuck E Cheese. Initially, it took them quite a while to complete a calendar but then they literally got a sticker everyday. It got too easy for them. So easy in fact I still owe them a trip to Chuck E Cheese (but I don't think they remember). I needed another reward system.