OK, I've now done two briskets: one with this recipe and one with just a simple rub following the Brisket 101. Here's my take.
My family LOVED this recipe. I thought it was very good, too. However, I can fully except the criticism that this recipe could be accomplished just as easily in an oven or a crock pot. You can smell the smoke, but you probably won't be able to taste it.
As for the Coke, use real Coke and not Diet or the Zero stuff. My guess is that even if you did use real Coke, something else is causing your chemical taste. Several brisket recipes call for Coke. Just my $0.02.
My second brisket was done the traditional "CookShack" way. The meat was not as moist, but the smoke flavor was excellent. I foiled from 165 to 201, then FTC'ed it for 3 hours. Unfortunately I did not get any bark or a smoke ring (even though I used a charcoal brickette). I served it with CookShack Spicy BBQ sauce on the side. My family loved it, too. But they want to know when I'm going to make the other recipe again. Oh well.
So I have a compromise. Next time, I'm going to split my brisket at 165, but this recipe on one half and leave the other alone. Then I should have some of both. OR I could just make the brisket the traditional way and serve the sauce from this recipe on the side along with BBQ sauce. Best of both worlds!