Ok folks here are two issues that come about when you "enjoy" these drinks, and bare in mind I have tried em all and ended up experiencing this.
1) Stimulants: When you use a stimulant you can think of it as "Borrowed" energy. They body uses food to manufacure energy by nourishing your adrenaline glands. A stimulant causes a temporary increase in adrenaline in your system which feels good and increases energy and focus for a short time. The downside is that if you take fat burners, drink energy drinks, go crazy with amphetamines etc you eventually "burn" your adrenal glands out and they get lazy - AKA next to nothing when it comes to natural energy that can result in chronic fatigue syndrome. This can take years to reverse, and only with a diet free of stimulants and nutrient dense food to nurish the adrenal glands back to health. THIS IS A BIG PROBLEM. Energy shouldn't Peak and Valley throughout the day. It should be stable without the need for stimulants.
2) Sugars: These are also employed to make these drinks not only taste good but spike you insulin levels and add temporary energy to your body's cells. Trust me, what goes up always comes down and while you can feel energized or outright cracked out these sugars reap havoc on your body. When you over stimulate your pancrease to constantly be producing insulin for these sugars (insulin allows the sugar in your blood to be metabolized) you end up with a situation where you can become a diabetic, and if you pancrease STOPS producing insulin you get to go straight to TYPE 1 aka insulin dependant requiring injections and medication that eventually leads to loss of limbs (amputations) and blindness with a shorter life span. High Frustose Corn Syrup is one of the mail culprits in these drinks and cause a specific kind of fat to grow on your liver, collecting other fats internally and clogging up the body.
I'm only writing this because I am a nutritional therapist turned affiliate manager who USED to drink these drinks SEVERAL times a day - not to freak you out but I thought you should know - I have been able to stabalize my own blood sugar, energy, and focus using nutrition and excersize.
It's a project that can save your life and make you MORE productive online - think about it.