The primary reason why coffee makes you sleepy sometimes is likely because it’s making you dehydrated. Coffee is a diuretic. In other words, it makes you need to urinate. Drinking it to stay awake can quickly lead to a vicious dehydrating cycle that actually makes you more tired.Click to see full answer. Also asked, does caffeine cause fatigue? Caffeine: An Energy Loan Shark What’s more, adds Dr. Teitelbaum, caffeine can worsen other mechanisms in the body that are leading to fatigue. “Caffeine actually aggravates adrenal exhaustion and low blood sugars, amplifying the anxiety and stress symptoms and fatigue,” he says. can caffeine not affect you? Your caffeine tolerance is affected by everything from what you had for breakfast to your genetics. Each person’s adenosine receptors are different due to genetics, and caffeine might not bind well with them. Folks who say caffeine does nothing to them probably do not have very “sticky” receptors. Just so, can caffeine help you sleep? Because caffeine is a stimulant, most people use it after waking up in the morning or to remain alert during the day. While it is important to note that caffeine cannot replace sleep, it can temporarily make us feel more alert by blocking sleep-inducing chemicals in the brain and increasing adrenaline production.Why do energy drinks make me tired?Having a high sugar drink to boost energy can actually make people more sleepy, a study suggests. But after an hour, people who had such drinks had slower reactions and more lapses in concentration than those who had a no-sugar, no caffeine drink.