Potion of booze
A non-blessed potion of booze will make you confused for 3d8 turns. ("Ooph! This tastes like liquid fire!") It will also provide some nutrition and abuse your wisdom. (10 nutrition if cursed, 20 if uncursed, 30 if blessed, regardless of dilution.) If the potion is cursed, it will make you pass out for up to 15 turns. If the potion is not diluted, it will also heal 1hp. A blessed potion of booze will not cause confusion.
If the potion was diluted, it will taste like "watered down liquid fire", and it will taste like "dandelion wine" if hallucinating.
Potions of booze are sometimes used in conjunction with the Scroll of gold detection on the Elemental planes to detect magical portals, or in conjunction with the scroll of enchant armor to prepare for the fire traps in Gehennom, especially by Monks and Wizards, but note that this is only useful with uncursed potions, since the desired effect is confusion.
Dipping an amethyst into a potion of booze will turn the potion into a potion of fruit juice. (This is a reference to amethysts' name coming from the Greek for "not" "drunk". See the article on amethysts for more detail.)
junk >> water >> sickness >> fruit juice >> booze >> blessed booze.
In dNethack, booze is actually useful as a source of nutrition. Drinking it gives 130 points of nutrition if uncursed, 140 if blessed, and 120 if cursed. However, drinking a cursed potion will cause you to vomit for 15+5d4 turns afterwards, possibly losing some of that nutrition. Booze will also heal you for HP equal to your level when quaffed, no matter the BUC of the potion.
Drinking booze now implements a "drunkenness" counter, which tracks the number of potions you've quaffed (BUC doesn't matter for the sake of the counter). If you are either stunned or confused (1/5 chance for confusion), and you've drunken more than three potions of booze total: You've got a
1/(number of potions drunk/3 + 1)
chance of not moving where you want to go. Again, this only triggers while confused with a 1/5 chance, so your chance of moving successfully while confused is 1/5*formula and equal to the formula while stunned. This applies to any source of confusion/stunning, not just from other booze, and doesn't affect your chances of getting confused/stunned in the first place.
In medieval Europe, the craft of beer brewing was greatly advanced by monks who had to survive long fasting periods.