Re:What to drink with your Favorite Hot Dog??
There's only one reason why they could have possibly associated Buttermilk with eating Hot Dogs in New Jersey, and that's because of Hot Dog Johnny's, which has served them with buttermilk for over 60 years. Other than that I don't know of any other place in NJ that serves hot dogs with butter milk, certainly not in my house.
As for me, and many others in North Jersey, being as how we are part of the "Birch Beer Belt" (along with Northeast PA), ain't nothin' like an ice cold Birch Beer with a hot dog.