Playing Microsoft Flight Sim or Civ VI isn't really gonna do anything for you. If anything, habits you pick up from a flight sim will just have to be unlearned when you get to flight training, if they're not already completely forgotten by that point. Staying in shape and studying that stupid packet with DISCIPLINE and the orders of a sentry is all you really need to do (and all you can do) to prepare yourself for OCS. I'd recommend enjoying your free time as much as possible, because managing a healthy work-leisure balance is also important for pretty much your entire career.Fortunately, my hobbies closely align with what might be helpful; working out, running, playing video games, and learning new skills. I'm one of those ass holes that can't just sit still - I know I will enjoy my time more if I I'm being at least a little productive. This could be playing simulator or strategy games, memorizing some pesky things ahead of time, or watching naval history movies.
Don't worry, I'll do my fair share of relaxing and wasting time before I leave. However, in my caffeine crazed energy surges, there has to be something you can think of. Has there ever been a time in training where someone had an advantage over you because they did 'x' or 'y' before they joined? Have you ever thought "given more time, I would've done much better"? Did you play a simulator game that might have helped a bit?
If you really cant think of anything then so be it - I'll take your advice, crack a beer, play some guitar, and see you in the fleet. Oorah!
If naval history movies interest you, then sure. I remember our OCS class towards the end of our time watched the Caine Mutiny and Mr. Roberts, but the movie I've referenced the most by far throughout my career is Dumb and Dumber, followed by Anchorman and Step Brothers. Lots of good quotes in there. As a P-8 guy, I also occasionally referenced Down Periscope and Hunt for Red October. If you're looking to go pointy nose, though, I don't need to state the obvious must-watch.
Ultimately, your relative performance in OCS has exactly zero impact on the rest of your career. Making it through OCS without DORing puts you at exactly the same start point as everyone else that does the same. As someone who was in the company that got one of the five or six banners, who was batallion staff instead of president or whatever else seems important there, I was average at API and above average at Primary. My performance at Primary was infinitely more important and relevant than OCS or API combined. And I didn't study a thing for Primary beforehand. I'd echo the recommendation for a single intro/demo flight at your local FBO, but other than that, don't sweat it. You'll easily pick it up when you get there.
My dad always likes to say, "What do you call someone that graduates med school at the bottom of their class? Doctor." I tend to think of OCS the same way.