Vodka is a carbon dosing method. You can use sugar as well. On my tank, 75G, I started out at .25ml a day of vodka for the first week, then bumped it up to .5 the next week, then up to 1ml the 3rd week and then slowly backed off.
What this does in a tank is the carbon dosing provides extra food for bacteria in the tank, making the bacteria numbers explode. When you have more bacteria in the water it will consume the bad nitrates/phosphate in the water FASTER than the algae can consume it, essentially starving out the algae in the tank. I had to do it because I had a type of red algae (not cyano) that was taking over my tank and only turbo snails would touch it, and I am not a big fan of turbos, so I chose the Vodka method instead. There are many articles and threads on ReefCentral about vodka dosing, enough to show it is far beyond the "Fad" stage and now considered normal and acceptable practice in certain cases. For me, it worked soooo much better than I could have imagined, so well that I have no doubt it works, and works very well.