FAB B and FAB B Lite are mostly ways to get a variety of posphate compounds, beef flavoring, papain (Adolf's Meat Tenderizer) and MSG into meat. The phosphates do what brine does -- hold onto moisture. I've never used FAB B or FAB B Lite, but have fooled around with phosphates -- especially tripolyphosphate. Which is most of what makes FAB work.
All of which is a way of saying the apple juice and beef sounds wretched. I use red wine, double strength beef stock, Worcestershire sauce, butter and seasonings in my brisket injection.
Like I said, FAB B and FAB B Lite already come with the buillion cubes in it. So you don't have to worry about adding beef. If you want to get an idea of what your mixers are going to taste like in the beef. Make some bullion and flavor it with your proposed mixer.
Some guys use beer,
What were we talking about?
Klose Steak Grill with Swing Set
Backwoods Fatboy with DigiQ II