If you work night shift, you know the wall. Somewhere around 3am, everything gets heavier — your eyes, your limbs, your ability to string a sentence together.
This lines up with your body's natural core temperature dip, which happens in the early hours of the morning regardless of whether you're asleep or awake. Your body is essentially trying to sleep whether you're letting it or not, and 3am is when that pull is strongest.
Because it's a body clock issue rather than a tiredness issue, more sleep beforehand only helps so much — plenty of well-rested night shift workers still hit the wall at the same time.
Some shift workers time a small amount of caffeine to land right around when the wall usually hits, rather than relying on one big coffee at the start of the shift. Neuchu works for this because it's easy to keep in a scrubs pocket or locker — 50mg per piece, ready when you need it. You can find it here.