You know that sudden crash about ninety minutes to two hours after coffee. It's not the caffeine itself, it's the fatigue signal your body was quietly building up coming back.
Caffeine doesn't actually wake you up, it temporarily blocks adenosine, the substance your brain uses to register tiredness. Once the caffeine clears, the adenosine that built up in the meantime is still there, and now it hits at once.
The simplest fix is spreading smaller doses through the day instead of one large coffee. When the crash hits, switching the sound around you or taking a short walk works better long term than reaching for another cup.