Ok I'm chronically sleepy at work principally because I'm an insomniac. Don't drink coffee because it will just get you feeling ultra-shitty and stimulated too much. I find it hard to get work done after drinking a lot of coffee. Here is my advice:

1. Start off the morning with some caffeine. I drink about 2-3 cups of tea.

2. Chew gum. It naturally keeps you awake.

3. If you have ice available, chewing or sucking on ice does wonders to wake me up.

4. Take a nap. No seriously, if you have a parking garage do this. Even a 30 minute nap in your car can do wonders. You might feel crappy after such a short nap but it's different from a caffeine crappy and it will keep you awake. I'm in meetings most of the day so it's imperative that I'm awake and coherent.

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Retro ...

I don't have problems about falling asleep at my job ( well on some rare occasions when I really went overboard the night before ) so I don't have much advise to give you there I just don't need the help

But a friend of mine who has a very hard time staying up at work spends his days drinking this fruit smoothie in a bottle drink.
I'll have to find the name for you.
It's a weird mix of fruit, algea and other natural stuff and keeps you up wonders.
And it's like 2 3 bucks for a 1 1/2 liter bottle. Comes in kiwi orange apple etc tastes. Taste takes getting used too but hey it's all about being healthy and not falling asleep