Beer Brand

What brand of birch beer is used in stores such as Pat's Philly Steaks and Geno?
I have noticed that many of them have a label clear that just says "birch beer" in a generic font. Obviously it has to be connected to a syrup of 2.5 or 5 gallon bag-in-box, but I have no idea of what brand of birch that is. It is very good and I would love to know.
What is Pennsylvania Dutch Birch Beer. A timeless classic Pennsylvania Dutch Birch Beer is a rich, creamy flavor with a hint of wintergreen that customers have enjoyed for over 70 years, and best of all free caffeine.
Battle of the Beer: Brand vs. Warsteiner