According to Official Guinness Records,
The largest alcoholic mixed drink is 686 litres (150 UK gal;181 US gal) and was achieved by Sultan Rashid and The Wine Drinker (both UK) at Urban Food Fest in Shoreditch, London, UK, on 23 June 2018.Members of the public helped pour 200 bottles of gin and over 500 bottles of tonic to make the drink.
For a complete list of 2018 records, please visit 2018 Guinness Records in United Kingdom.