Unusual DIsclaimer: I don’t recommend extracting DNA in this manner. As another blogger pointed out, there isn’t much you can do with DNA extracted in this way. You can also use rubbing alcohol in place of vodka.
I saw this on the International Society of Genetic Genealogists (ISOGG) Facebook page, https://www.facebook.com/groups/isogg/ – you have to be a member of ISOGG (membership is free and you don’t have to do anything after you join). The link is https://www.bbc.com/news/av/science-environment-21184523/professor-brian-cox-isolates-his-dna-in-experiment. A quick search of my least favorite search engine came across several similar articles, https://www.wired.co.uk/article/extract-dna (2014 article); https://www.futurelearn.com/courses/discover-dentistry/0/steps/7202 (didn’t see a date), https://www.popsci.com/how-to-extract-your-own-dna (2016 article), https://www.express.co.uk/news/science/1071497/DNA-how-to-see-DNA-washing-up-liquid-isolate-DNA-Brian-Cox-experiment (2019 article). You can also type in “extracting DNA using vodka” in your favorite or least favorite search engine. There are some YouTube videos as well: https://www.youtube.com/results?search_query=extracting+DNA+using+vodka.