I use a system of ‘Chance cards’ in the classroom. These are business card-size photocopied pieces of paper that have ‘chance card’ written on them and ‘name’ for the children to add their names.
If the children win a Chance card (through ANY good behaviour, good work, or nice smile!), then they write their name on it and put it in a box. At the end of the day, one Chance card is pulled out, and that person receives a sweet.
Start all over again the next day. Works very well and is very cheap to maintain! I tend to hand them out to tables that have settled quickly, tidy tables, good answers (sometimes ANY answers!) and so on.
This can be developed: there can be a Daily Chance Card Box, and at the end of the day, these go into a Weekly Chance Card Box. On a Friday, there could be a grand draw of 5 names, and then the chance cards are added up by a child and monitored. This system works especially well when doing supply, as you can focus right from the start by announcing that you have a special treat just for this wonderful class that you’ve heard about! No more supply baiting!