Scavenger Hunt
You should not have any problem getting your child to clean their room if you provide them a motivation. It can come in all forms, but we doubt that anything will be more effective than monetary compensation!
To Each His Own
Do your children have a tendency to retrieve new cups from the cupboard when their old ones remain unwashed? If so, get them their very own magnetic cup. Since they stick to the fridge, they cannot give excuses about being unable to find them!