Kids might not think that hygiene is a good enough reason for washing their hands, but the prospect of receiving a toy can sweeten the deal.
In South Africa, rated by the World Health Organisation as one of the worst countries for personal hygiene, thousands of people die each year from preventable diseases such as cholera and typhoid.
Many are children and teaching them to habitually wash their hands could stave off these illnesses.
To encourage children to reach for a bar of soap whenever their hands are dirty, the agency Y&R Zambia - working with organisations The Safety Lab, Dare to Share, and Blikkiesdorp 4 Hope - invented the "Hope Soap".
It is a transparent bar of soap with a small toy inside - a tiny car, a Hello Kitty figure - that kids can get to only by washing their hands repeatedly.
Launched last year in Blikkiesdorp, a poor settlement outside Capetown, the Hope Soap has already shown considerable results. According to Y&R Zambia, it has reduced illnesses in the community by 70 per cent.