"Bad vodka is almost a bit embarrassed to be on your palate. You can feel it trying to slink away, slightly embarrassed and apologetic. It feels thin—you swallow it, you forget it. A lot of distillers can and will use sugar and glycerin to enhance the texture, or to improve the sensation of the spirit, or the smell or taste of the spirit. But that makes for a bad vodka, a spirit with no credibility."
How Can I Spot a Bad Vodka?