A drinking barrel is build just like other furniture (tables, chairs and the like). Its just a plain barrel you select from the list.
After a Barrel is build it has 2 Options:
[r]oom: you can design a room from it, this will act as dining hall just like from tables
[a]dd mug: you can store up to 5 mugs on the barrel
dwarf will automatically refill the empty drinking barrels with aviable drinks from the food stockpile (food hauling for the occational dwarfs activated of course), the drink barrel will hold up to 5 drinks.
if the barrel is in a private dining hall, the owner dwarf(s if married) will get his drink from this barrel, restricted for other dwarfs
if in an meeting hall (public dining hall) any dwarf will go for it then thirsty
if no mug is present the barrel is not useable for other dwarfs in the moment, just like the drinking from the stockpile
the dwarf will take the mug and one drink, randomly approches a tile inside the (designated) room and start drinking, after he finishes he will haul the mug back to the barrel.
military dwarfs will automatically fill their waterskins at the barracks they are allowed to do any of the 4 options (sleep, train or store personal/military equip)
the same with the food cabinet: it uses the normal cabinet just instead of storing clothing its for storing prepared food (only!), can hold up to 5 prepared food
just it doesnt need the mugs
it basicly acts like a local food storage
the basic idea behind this suggestion is to give mugs and goblets some use, while keeping your dwarfs from cluttering the food stockpile.
so you can make personal rooms filled with food without managing nasty stockpile infos, or getting the food stolen form a nearby hungry dwarf. drinking barrels and food cabinets a dwarf is allowed to use will have higher priority than the food stockpile, but he still will go for the stockpile if all barrels are occupied or empty.
EDIT: the qualiy/material of the goblets/mugs used will give the dwarfs happy thoughts. so a Granite mug will give maybe just +1 happiness, while a *<*platinium goblet*>* will give him quite a boost (up to +10?) artifact mugs/goblets will always give +15 ... also the stored mugs will count to a rooms value.