What entitlements will I receive as a single E-6 living in the barracks in Grafenwohr, Germany?

For starters, the army isn’t Burger King, you don’t get to have it your way. You will live in the barracks because you are on an unaccompanied OCONUS Tour. It’s not like Hawaii (E6 get BAH). If you were married, you would receive OHA which is for married or E9, and O3 and above unaccompanied. You will have a meal card to use at the DFAC. You will get COLA which is around $140.

I know unaccompanied E8’s living in the barracks in Germany

Last first. Graf and the surrounding area does not have a lot of available housing. They are a cluster of very small towns near by, generally built to support cultural needs. You will receive cola, you will likely be on a meal card. Taxes depend on your state, not the military, you will need to check your state website. You will pay Federal Tax. Aside from Cola, and maybe a break on state tax, that is all.

It is a great assignment, with a lot of things to do, site seeing some of the best in Europe, sports, cultural opportunities abound.

I'm not sure about the meal card question, so I'll defer to others on that. You will still pay state and federal income taxes. You pay these anywhere you go in the world unless it is a designated Combat Zone Tax Exclusion (CZTE) area.

AR 420-1 covers Army Facilities Management (housing policies). BLUF, for CONUS (incl. Alaska and Hawaii) E-6 and above can live off post, for OCONUS it's E-7 and above unless restricted by the Garrison Commander. I suggest you check with the Housing office in Grafenwoehr to get a copy of their policy or see if you can find a copy of the policy letter on the Garrison website. Generally, it simply comes down to money. If there are rooms available, you will most likely need to stay on base. Usually when they hit the threshold of 90-95% occupancy is when they allow individuals to move off-base. If E-7's are staying on base they would be in SEQ housing, not barracks. Again, goes back to that Garrison CDR caveat, in overseas locations they can mandatorily assign personnel to Army housing. This is the same for personnel with families too.