Look at the nutrition facts label, see how many grams of added sugar there are, and to keep things simple set the the tax at one cent per gram of added sugar. I can't see this being hard to implement.
It's not one of the extremely rare Giffen goods which defy the laws of supply and demand. Most alcoholic drinks have a substitute in drinks with less (or no) alcohol in them, competing on price. Moreover, people's consumption is affected by how much is considered "normal" to drink (one of the early, solid findings of alcohol epidemiology), so there's a positive feedback amplifying small changes to consumption habits from other things.
In countries where the alcohol tax is high enough it reduces alcohol consumption but massively increases sales of sugar and yeast.
Take a look at Canada's consumption numbers and see if the "sin tax" accomplished anything.
We don't have that. But we have other countries and times to compare through, and there really is no question that accessibility affects consumption.
These are massive corporations targeting individuals. If you look at obesity rates people are clearly on the losing side here.
The bulk of US sugar comes from "HFCS" (high fructose corn syrup) which is HEAVILY subsidized in the first place.
So taxing something you are subsidizing makes zero sense.
Remove the subsidy and the price of corn will go up, and with it the price of HFCS.
I also like your idea of keeping things simple. The hard part, as always, are the edge cases. If the tax is associated directly with sugar in some manner than diet sodas won't be taxed. Another possible albeit silly argument is why not tax sugars in fruit?
Note: Im a software engineer. Not a dietician. I really don't know a detailed difference between artificial sugars and natural sugars or how our bodies process them.
Because total sugars and added sugars are not the same thing. It makes more sense to tax added sugars because they are clearly worse, and it strains Medicare/Medicaid budgets.
Adding grape juice or apple juice to a snack or drink would still be considered an added sugar on the nutrition label under FDA guidelines[1].
The reason they do that is often to make sure "sugar" isn't the first ingredient in the ingredient list, which have to be listed in decreasing order of weight[2].
Note that the ingredient list and the nutrition facts label are two different things.
1. https://www.fda.gov/food/new-nutrition-facts-label/added-sug...
2. https://www.nia.nih.gov/health/how-read-food-and-beverage-la...
Running with this idea, there'll eventually be a federal conversion table where any given chemical would be translated to their mass in sugar. From there, tax calculation's simply:
sum((sugar_conversion_lookup[ingredient] * mass) for ingredient in product) * tax_per_gram_of_sugar