Argonian Ale Extraction

Summary
If you wish to keep the bottle of Argonian Ale for your personal collection, you can always steal it from Brenuin after the quest is completed. If you have a high enough Mercantile skill, you can also sell it to a shop vendor, then re-buy it to negate it's stolen status.
 * Quest Giver: Brenuin
 * Initiated by: Asking Brenuin if he is always drunk

Heres a list of all Alcoholic Beverages found in Skyrim

Walkthrough
Brenuin will tell you there is a rare bottle of Argonian Ale in the kitchen of the Bannered Mare and ask you to steal it for him. You can find the Ale in Bannerd Mare on the left door inside the house (in the kitchen in The Bannerd Mare). It is relatively easy to obtain, there is usually no one in the room to catch you taking it, but if there is you can simply carry it upstairs and take it there, where there are no witnesses.

Rewards
Potion of Vigorous Healing or healing potion based on level.