You probably already have a Brita filter that your roommate or significant other bought you. Why just use it for making your tap water taste better, when you can use it for something really useful, like filtering vodka. Don’t spend $20 for decent vodka when you can buy the cheap stuff and turn it into something tolerable. Save yourself $10 and purify it yourself using a Brita filter.
If you want to make Brita filter vodka you have to understand that you will not be able to turn a bottom shelf vodka into Grey Goose, Ketel One, or other top shelf liquor. You will however make it much more bearable to drink, taking a bottom shelf vodka and turning it into something without the nasty taste and the need to gag afterwards. A Brita filter is essentially a carbon filter and by running vodka through it you will be doing the same type of filtration that is done more extensively on the top end vodkas, albeit on a smaller scale.
First start with a cheap vodka. For best results, go for something just a step above the absolute cheapest vodka you can buy (Nikolai Vodka is too cheap). Cheap vodka tastes bad not just because it isn’t filtered many times, but also because it is made with cheap ingredients (which filtering won’t be able to solve). Something a slight step up from the bottom tends to give you the best results (Jacquin’s Vodka works well).
Set aside a filter just for vodka. Once you filter vodka through the filter, you will never get the taste out of it, so keep one filter for water and one for vodka (you can use the same pitcher just clean it well afterwards). The standard brita filter pitcher will hold a regular sized (.75 liter) bottle of vodka.
Pour the vodka into the top part of the brita filter and let it filter into the bottom part as you would normally with water. It will take longer than water though, so be patient. When the vodka has worked its way through the filter, pour the vodka into a bowl or another pitcher and filter it again. For best results, it should be filtered at least three times. You can filter it more times than that but the difference will begin to get smaller and smaller. Taste it after a few filtrations until you find it to be adequate.
When you’re finished, pour the vodka back into the bottle (a funnel will be a big help here). If you’re really crafty you can pour the filtered vodka into a nicer vodka bottle and your guests will be none the wiser. Take out the filter that you used for the vodka, put it in a zip lock bag, and put it in the refrigerator until you want to use it again. Be aware that filters used for vodka will not last nearly as long as those used for water, but filtering the vodka yourself is cheaper than buying expensive vodka, even after the cost of the Brita filter. You can also filter other clear liquors, like clear rum, and get similar results (don’t try it with gin though as you will lose most of the flavor too). Enjoy!