By Lydia Stephens If you struggle to convince your child to eat healthy fruits and vegetables instead of high sugar and salt snacks, we may have found the trick for you. Marketers know exactly what they are doing when they fill the packaging of a child’s snack cake with popular cartoon characters. Why would a child eat a plain old apple when they can munch on a chocolate cake that is wrapped in their favourite colourful cartoon? Now one dad has come up with the ultimate hack to encourage his kids to eat fruits and vegetables. In an Instagram video that has more than nine million views, Utah da…