They can throw all kinds of nasty and or synthetic crap into something and call it vodka.
I'd be interested actually to see how you fair with Gzhelka as opposed to Crystal or Stoli Gold. Gzhelka is reknowed for its taste but is made using a lot of average quality tricky ingredients that give it a high end flavor and a low-mid end price tag.
I had some cheap vodka once(plastic bottle)that was horrid.
Most booze gets a literal more tolerable after a few shots but this stuff was like paint thinner.
Worst tasting stuff I think I ever had.