I'd also support them from a Pigovian tax point of view - the extra tax on these activities can be used to offset the excess healthcare costs associated with obesity, alcoholism, smoking, etc.
I am not economist, but that sounds like a reasonable idea. Kind of like the sugar tax on soft drinks.
I would also think that the purpose of sin taxes is not to discourage the 'sins' but to produce a consistent stream of revenue for the government. When you have a large user base who's addicted to alcohol, cigarettes, and so forth you have people who are going to pay that tax regardless of how high it is. Look at the price of cigarettes in much of the United States. They're more than $10 per pack in much of the country, and most of that is tax if I'm not mistaken and smokers will find the money to smoke somehow.
The only exception being Coca Cola Classic which has a specific recipe that can't be changed.
I've been in the soda aisle in the grocery store recently and I can tell you that is not the case. Pepsi, RC Cola, and all the store brand colas and all the other sugared drinks are still very much in effect. Energy drinks are also still the rage where I live.