Dr Pepper Mesquite Marinade

I had a bottle of this and a small brisket I needed to cook. Thought what the heck let's try something different. The Dr. Pepper BBQ sauce wasn't half bad. I opened this and it smelled good. Poured on my brisket to marinade.

Make a long story short it was horrible and I chucked the brisket. The taste was not very good. It started to harden the outside of the brisket, especially the thinner areas.