Martini
There is only one respectable drink for a DM: The Martini. I mean a real martini which is just gin, a little vermouth, and an olive; nothing pretending to be a martini or ending in -tini. It is the most just as planned of all the drinks. Simply picking up a martini glass kills a little bit of your soul and lets you sink even lower into vicious disregard for your players. Other drinks promote camaraderie. The martini doesn't care. It doesn't fudge rolls. It doesn't give tip offs to trapped chests and cursed items. It is death-by-neutrality with an olive.
How to make a proper martini
Ingredients
55ml gin
15ml vermouth, dry
1 olive on a pick
1 standard (13.3cl) cocktail glass, chilled
1 standard mixing class
Crushed ice
Preparation
1: Pour the gin, vermouth and ice in the mixing class
2: Stir well. The International Bartenders Association employs a squad of hitmen that kill anyone who tries to shake a perfectly servicable martini
3: Serve in glass, add olive. If you are a godless heathen you can replace the olive with a lemon peel
Variants
It is said that the martini is improved by making it dry; adding less vermouth to it or none at all. There is the English variant (as suggested by playwright, actor, singer and all-round classyman Sir Noël Peirce Coward) where one "waves [the glass] in the general direction of Italy". Another is the Spanish variant (as described by Luis Buñuel Portolés, famous for the movie Un Chien Andalou, sixteen minutes of pure WTF including a scene where a woman's eyeball is cut open with a razor blade) where one holds a glass of gin next to a bottle of vermouth and let a beam of sunlight pass through. Winston Churchill is said to have whispered "vermouth" to every glass of gin he was about to consume, likely to intimidate the gin into becoming a martini.
The inferior version to the martini is the gibson: prepared as above except with 60ml of gin, 10ml of dry vermouth and a pickled onion. But if you are a real man, you drink the martini.