The reason why the busier you drink, the more tired you become

 When we're active, our cells release energy and produce adenosine, a substance that builds up and makes us feel tired. Adenosine attaches to cell receptors, signaling them to slow down and causing drowsiness. During sleep, adenosine levels decrease, and we wake up refreshed. However, caffeine can temporarily block adenosine receptors, delaying the tired feeling. It works by filling the receptor spots without triggering the drowsy signal like adenosine does. 

There's a catch: while caffeine can make you feel more alert and energized, it's not actually creating new energy, but rather borrowing the feeling temporarily. Caffeine blocks adenosine, which causes drowsiness, but this effect is only temporary as the caffeine wears off and the accumulated adenosine takes over, sometimes causing a sudden wave of sleepiness.

In short, caffeine creates a debt that must be repaid eventually, and the only way to do so is by getting some sleep.

How to Drink Coffee Healthier

When you drink caffeine matters. The amount of adenosine in your system and how tired you are affects how well caffeine works. Late-day coffee may feel stronger, but it can make it hard to fall asleep at bedtime. Caffeine's effects last about five hours and vary between individuals. Regular coffee drinkers may build up a tolerance to caffeine over time, making it less effective.

Caffeine increases cortisol, a stress hormone that boosts alertness, so it may feel more effective later in the morning. Sugary coffee can worsen the energy crash after the sugar rush. Drinking coffee after a meal can slow down the caffeine's effects.

Tea, energy drinks, and other caffeinated beverages work similarly to coffee, but each has its own set of additional compounds that can enhance or modify caffeine's effects. While caffeine can be helpful, it's not a cure-all. To energize ourselves, we also need sufficient food, water, and sleep.