I have an extremely high caffeine tolerance from a couple decades of absurd amounts of caffeine consumption. I usually take a generous scoop of pre workout (Kaged, Jym, or Peri) along with a coffee before my workout in the morning and I could and have gone to sleep after and once during. I also have no noticeable response to the occasional energy drink I consume. Is there a way to re-sensitize yourself to the effects of caffeine so that pre workout is actually useful again?
Sure, just stop using caffeine for a few weeks.