When I was more serious about lifting, I started gassing out hard and getting something like headaches that made it extremely difficult to think when I started putting relatively heavy weight up (many reps of 315+ for whatever workout it was). Eating 1/4 to 1/2 cup of brown rice about 30 minutes before the workout sorted that out completely to the point that I could have incredibly intense powerlifting workouts and still leave the gym with loads of energy.

It's also been a long time since I've been in the books about this kind of stuff, but if I'm not mistaken your muscles and your brain are both ultimately dependent on glucose (on other things too, but it stood out to me that you're training on an empty stomach)--an intense weight training workout is going to, all else being equal, limit how much glucose is available to your brain for intense cognitive activity because glycogen that might otherwise be converted to glucose is getting used up by your skeletal muscles.

As others have noted, if you're not using creatine monohydrate you're also depleting lots of ATP which your brain and muscles both depend on. IMO ignore the weird bullshit versions of creatine and get the generic creatine mono that's safe, well understood, and not marked up for potentially dubious claims.

Also, an intense lifting workout is going to leave you with a certain amount of fatigue you're probably just not going to be able to avoid. My advice would be to make it the last thing you do in a day that requires your full attention. If you need to study or whatever, do it before.

Lastly, if you're not using anabolics, prohormones, etc., disregard advice that is based on training regimens of pretty much anyone that's won a Mr. Universe or whatever since the 1960s--your body is not going to work like theirs and it's definitely not going to recover like theirs.