Buffalo Bills Lineman -- BUSTED FOR DUI ... After Puking From Car Door

Buffalo Bills defensive lineman Alan Branch was locked up for DUI this weekend -- after cops say he was so drunk, he was PUKING out of the driver's side door of his car.

Branch -- who's entering his 6th year in the NFL -- was popped in upstate New York around 2am Saturday morning.

And if the alleged puking wasn't a dead sign of DUI, cops also say the 6'6", 325-pounder had a blood alcohol level of .14 ... almost TWICE the legal limit.