Taxes imposed for the purpose to impose an opinion then curb human behavior is unconstitutional where there is no rational bases that can otherwise be established concerning common law standards for health, safety, or welfare.  If not so, then we wouldn't need to avail upon the power to tax.  All we'd have to do is repeat prohibition without reason for health, safety, or welfare.  I've never drank alcohol beverages and don't drink canned juices or pop.  I'd love for them to be illegal, because I'm tired of my rising insurance premiums even though I've not visited an MD for several decades now.  I believe that there is enough public safety data for government to defend a prohibition on defined alcoholic beverages, and public health data defending a prohibition on defined processed sugared drinks.  But, as you point out, FAT chance in our obese and diabetic society.