I'd also be interested to know about the flavoring used. It seems like this would run afoul of the US labeling laws for vodka, which require it to be "without distinctive character, aroma, or taste". This technicality of course doesn't mean that it's not done exactly as Andrew describes.

Here's a couple background articles on the bottler's role, without specific reference to flavorings:

http://adiforums.com/index.php?/topic/452-whiskey-bottling-v...

http://www.bbc.com/news/magazine-18360315

> It seems like this would run afoul of the US labeling laws for vodka, which require it to be "without distinctive character, aroma, or taste".

That seems improbable because flavored vodkas are common.

That rule is specific to products labeled "Vodka".

Flavored vodka has to include the flavor on the label. Pages 2 and 11:

https://www.ttb.gov/spirits/bam/chapter4.pdf

Ah. Well, what can I say? I can easily tell the difference between different vodkas in blind tastings, though I can't necessarily tell you which is which. But my wife can consistently pick her favorite vodka out of a blind lineup.