VODKA on a budget

So my OS class today covered a drinking tip I'm going to try soon. Grey Goose is good vodka but it's expensive. Cheap vodka is cheap, but it leaves a bad taste in your mouth. Where does the bad taste come from? Impurities in the vodka. How do you remove the impurities? A Brita filter of course! Filter it once, still tastes bad. Twice, better. A third time, perfect! And just as good as the Grey Goose. We'll see.