With my 9/10 year olds, I used to pick out those who are successful in doing in the drill to be demonstrators – so they have a moment of pride there. I don’t usually get the same people, because there are the outstanding ones who would usually do better than the rest. This helps motivate the rest to want to do better.
With my 11/12 year olds, many times when we do a drill or play a game, I’d tell them that they would get to leave training 7 minutes earlier than the rest if they “win”. This motivates them as groups to complete the task, or score more goals, in order to “win the challenge”.