This is because children are at the stage of developing where a unhealthy diet really affects the growth process of the children. Therefore, No soda should be allowed till the child grows up and when the child finally gets to drink, Self management of controlling the amount should be taken into considerations for health reasons.
They should be allowed to drink soda provided that they can control the amount the consume. To me it is fine to drink during huge celebrations as huge celebrations don’t often happen. By drinking only during huge celebrations we can also keep track of how often we drink it. This way it will be controllable.