It's more dangerous than people realized in the past. Sodas are not just terribly unhealthy, they contain caffeine which can be addictive. Many kids are drinking enough of them to develop type 2 diabetics in childhood, something almost unheard of twenty years ago. The chemicals in the drinks also cause concentration problems, behavior problems, aggression and hyperactivity. What's more, the chemicals are also known to exacerbate current medical conditions such as asthma, epilepsy, ADHD, bed wetting and so on.
Why would it be okay for anyone to drink something like this, let alone children. A child's body is smaller than an adults so it takes a far smaller number of chemicals to get a far bigger reaction.
Soda provides no positive benefits whatsoever.