I've brought beers along for gravel grinders before (and road rides, and mtb rides) I would suggest you avoid stouts and porters. Riding right after drinking one can be somewhat unpleasant. IPAs are nice but lighter beers are what work best. I hate to admit it, but PBR is actually a good mid-ride beer.

And you may want to put your beer in a can koozie, they serve a triple purpose: they keep the beer cooler, they keep the cans from banging around and they keep things discreet.

If your bike doesn't have bottle mounts (and even if it does) I suggest looking into a frame bag like the Revelate Designs Tangle bag. You can put a hydration bladder in it and get some weight of your back, keep food/arm warmers/phone within easy reach. And you can fit a six pack