Sometimes that 3 o'clock feeling starts way before the usual afternoon slump -- and sometimes it lasts longer than quitting time. A good night's sleep is a great weapon against that sluggish feeling, but sometimes it's not enough. Pesky energy zappers are hiding in your everyday routine.

Luckily, you don't have to knock back three shots of espresso or chug a neon energy drink to snap out of zombie mode. Try these super-simple fixes that defeat energy zappers by naturally boosting your energy levels -- without the jitters and sugar crash.

The Reason: Ever wondered why sitting in your car then transitioning to sitting down in your office chair can feel so utterly exhausting? According to Dr. Frank King, M.D., founder of King Bio, sitting for long periods of time puts your body into idle mode. Your lack of movement makes circulation sluggish and lowers the amount of oxygen flowing to your brain. Cue the onslaught of yawns.

The Fatigue Fighter: Go for a walk. Studies show getting up and moving can boost energy for up to two hours. "Walking is the simplest, most natural form of exercise," says King. "Taking brisk, 10-minute walks a day helps increase circulation, lower blood pressure, and instantly perk you up." Getting out in the sunlight also boosts your serotonin levels so you come back to your work refreshed, more productive and even more creative.

The Reason: The reason you feel too zapped to clean up your cluttered desk or office home? The mess itself. "Not only is there literally less space to do your work, create your art, make a magical spreadsheet, etc., but all the stuff is staring at you, reminding you of the hundred other things you have to do," says Los Angeles-based clutter expert and professional organizer Fay Wolf of New Order. "Your clouded brain isn't able to be fully present to the work at hand." Looking for your notes from that one meeting or your favorite pen wastes time and tires you out before you've even started.

The Fatigue Fighter: You've heard that the bedroom should be reserved for two activities: sleep and sex. Well, according to Wolf, your desk should be reserved for current work projects and the tools that facilitate that. This means your computer, materials relating to your current project, a few writing utensils, and a small amount of office supplies like a notepad, a stapler, scissors, tape and paper clips (unless you have room for those in a desk drawer) can stay. Everything else is having a judgment day.

"Go through every item, left to right, and either discard it or choose a new home for it," says Wolf. "If a piece of paper needs to be filed, make a file for it: 'To Read,' 'To Pay,' 'To File.' Next, she suggests using a to-do list app that you check every day and where you write down absolutely everything that has to get done. "If anything has a deadline, add it to your trusted to-do list."

The Reason: This meal can make or break your energy reserve for the rest of the day. If it's way too large (like Sunday-brunch status) you'll be left feeling sluggish, and if you forget to eat it in the first place, your metabolism will never get that wake-up call.

"People who eat a balanced breakfast have more energy, perform better at school and at work, and sleep better at night, which means they wake up the next day more energized," says Elizabeth Somer, M.A., R.D., author of "Eat Your Way to Happiness." But Somer isn't talking doughnuts and coffee.

The Fatigue Fighter: For a winning breakfast to fuel your energy, follow Somer's 1, 2 ,3 rule. The breakfast must have:

1) whole grains, which provide high-quality carbs for the brain during the morning hours,
2) a little protein to keep you satiated and maintain your blood sugar level throughout the morning, and
3) one or two colorful fruits and vegetables.

Try a bowl of whole-grain cereal with low-fat milk and a handful of berries on top with a side of sliced watermelon, or make a smoothie with fruit, soymilk and wheat germ.

The Reason: You may not feel like you're walking through the Sahara, but there's a good chance you're mildly dehydrated right now, and even mild dehydration makes you feel sleepy and sluggish. "Many of us walk around dehydrated without realizing it," King says. "Dehydrated bodies trap toxins and encourage water retention -- a natural defense against the chronic 'drought.'" Remember, your body is about 60 percent water, and there's no way it can function at its optimal level during a drought.

King's simple test for dehydration: Pinch the skin on the back of your hand and hold for three seconds. When you release, if the ridge from the pinch remains for more than a second, you're probably dehydrated.

The Fatigue Fighter: Next time you're feeling drowsy, chug a glass of cold water for an instant fix. Then, take a look at how much water you've been drinking. According to Dr. King, you should aim to drink half your body weight in ounces of water every day. If you weigh 150 pounds, that's 75 ounces of water (about 9 cups). If you want something more pleasing to your palate, snack on watermelon, which is about 91 percent water.