Seriously. That’s all.
But it’s not the only thing you can do. Take 4 good, deep and slow breaths. Look out a window. Pinch your shoulder blades back, down, and together as you look up to the ceiling. Raise your arms overhead a few times as high as they’ll go. Make eye contact with a friend, share smiles, and realize how good it is to take a micro-break from whatever it was you were just working on. Doing these things will instantly make you feel more alert. You don’t need to keep a steady dose of caffeine in your system to feel awake. Realize that you are tired because you are probably exhausting your brain by drilling into one (or many) tasks but also being so sedentary, your brain and body also want to go to sleep.
Our workflows, environment, devices, and tasks are all rapidly becoming more efficient at tricking our brains to focus purely on them alone. As a result, we forget to shift our posture, drink water, blink, or even breathe sometimes. Our metabolism slows way down, our muscles get tight, and stress hormones can rise.
So, do yourself a favor right now.
Leave your coffee on the desk.