My worst brew sessions have been when drinking, too. A buddy of mine and I brewed up a Belgian Stout (which has an odd flavor profile to begin with if you aren't used to it) and thought it would be a good idea to add some absinthe to it. The real deal absinthe, Suisse Le Bleu #4, tasted like liquorice ouzo. What could go wrong... Stout... liquorice.... yum right?
After bottle conditioning, we cracked open our first bottle and it went from being this drinkable Stout to this horrid nasty bitter liquorice fluid with Belgian funk. It was the grossest thing either of us had ever drank without tasting infection. We named it the "Belgian Strong Weird" and proceeded to dare other brewers to drink it. It tasted like Belgian tire water flavored with anise mosquitoes. Dank and disgusting.