The very first post here at Dave's Cupboard when I started the blog in 2006 was about the Russian beverage tarkhun (тархун), a soft drink based on tarragon extract. Tarkhun is very popular in Russia, and there are several companies that produce, bottle, and import it into the United States. Each brand has it's own original formula and because of this, each brand has its own distinctive flavor profile. For the most part, though, they all have about the same shade of green.
In the local Russian supermarkets here, there are three readily-available brands of tarkhun. We've tried all of them, and here are our impressions of each of them.
Rosinka is Lynnafred's favorite tarkhun. This is partially because it was the first one she'd ever tried and partially because it's the brand that is the most like an American soft drink. Rosinka has plenty of carbonation, is somewhat sweeter than the other brands, and has a mild tarragon flavor with slight notes of citrus and licorice (fairly typical of tarkhun, actually.) It's sold in a variety of sizes, including 1- and 2-litre bottles.
Ostankino Drinks - This brand of tarkhun is more fragrant and herbal than Rosinka.but still sweet and fizzy. There are notes of licorice and vanilla and just the smallest hint of a medicinal quality, kind of like the one you get with a Riccola herbal cough drop. Ostankino actually makes two varieties of tarkhun, one bottled in plastic and one bottled in glass which they call "Ostankino Drinks Extra." I haven't been able to tell the difference between the two except that the plastic-bottled variety seems to go flat faster after it's been opened.
Napitki iz Chernogolovki - bottled by Russian beverage giant Ost Company, this brand is strongly herbal-tasting, almost to the point of spiciness. It is by far the brand most like an old-style "tonic" beverage and least like a modern soft drink (not to say it isn't sweet and carbonated, just that this tarkhun might be more of an acquired taste for Westerners unfamiliar with the beverage.)
Finding tarkhun near you: Although everyone I know who has ever tried it likes it, tarkhun has never really caught on in the US, and there are no domestic bottlers here that I know of. It's unlikely that you will find it in any mainstream supermarket or convenience store, either. Look for ethnic Russian or Eastern European markets near you - that will be your best bet.