Taxation is a clumsy, costly (administration overhead) and unlikely to be effective. What we are seeing is naked politics.

Sugar is uniquely addictive and uniquely destructive to metabolism and body tissues. But taxing addicts, who tend to be poorer, is as likely to make them wean off sugar as trying to get opioid addicts stop by taxing their opioids. Addicts are price insensitive. 

The damage from the calories model of nutrition and soft drink propaganda, like it being okay to consume sugar if you move more, has been done. We've lost a generation and probably more with epigenetic effects. What a sugar tax might accomplish is reduce the number of people who become addicts in the future.