Soda Tax - Where fiscal policy meets moral stewardship

Governor David Paterson's proposed 2009-10 budget for New York state includes a variety of new sales taxes, including one on soda. This is not the first time a government has used fiscal policy to administer their morality. In Canada it is common to tax tobacco and alcohol heavily to offset the costs of the health care system. In this case it seems warranted since those who consume such goods tend to use the health system more often. In Canada the proposed 18 percent soda tax would have some merit for the same reason. Especially considering obesity related diseases, such as diabetes, may cost taxpayers more than the diseases related to smoking and drinking.
But in New York where there is no government health care, is there merit for specifying a particular good for higher taxes?
Certainly taxing 'bads', such as carbon emissions are a different matter. Everybody has to share the burden on utility when such 'bads' are released even though only a few people are responsible. So if a few people pollute the drinking water to produce their goods, should they not have to pay to clean the water instead of taxpayers-at-large?
Is this tax arguing that fat is a public bad? Everybody has to see it but only a few get the joy of over consumption? No I don't think so. That seems too ridiculous to be true.
Is there a way to evade taxation? Perhaps. Right now if you go to a fast food establishment you can get a 'meal'. Buy a burger and add fries + soda for $1.99 or something like that. Now what if they changed the menu to say 'buy a burger + fries and get a free pop'? Would that reduce a customer's tax burden by a 25 cents? Seems like there could be quite a few loopholes to be exploited.
With State budgets across America stretched, and New York having one of the largest deficits, perhaps this is more about the money than trying to force people into shape. This more simplistic argument gains barrings when you consider new taxes on health clubs and massages. Both, I would wager, have net benefits to people's health; both physical and mental.