I do provide these types of incentives, but always useful gear or a learning tool. As I have known many of my scouts since they were born (I am referred to more often as "Uncle" than anything else), I give them these types of birthday and Christmas presents as well. Acknowledge and reward good behavior, strong effort, and successful work. Do not reward unsuccessful work, but spend the time with that scout to make them successful. Be honest about failure, but show them in detail why it failed and how to do it better. In many cases, just showing the honesty of addressing failure, and the care to make them successful will win over the scout, without any reward. I have had some scout complain to me that I spend too much time with the less successful scouts, and I just respond to them that they should be spending the time with them as well. The troop succeeds or fails as a troop, and it is in all of their best interests to make everyone successful. Some parents are actually more difficult to manage with this though.