I agree with Jennifer...stay away from the sugar.
Now here's the part where I should hang my head in shame. I'll admit that I'm a caffeine addict. I have been hooked on caffeine since I was a little girl. My mom use to give me tea in a bottle. I've been having caffeine for a long time. Sure I've kicked the habit a few times but then I smell the coffee and I'm off and running. I have to have some of it.
I have been honestly limiting myself on the coffee. Some of you are going to be amazed at this but others are probably right up there with me when I say I make coffee in the morning and fill the pot up to the 8 cup line. That is equal to two of my mugs , we wont talk about how big the mug is. That's usually my limit on the coffee for the day.
Now, diet Mountain Dew....that's another story....it's ugly!!

and we wont go there right now
I personally think everyone is different I've taken the caffeine out of my diet and didn't lose any better on Atkins. Yes, he does say that we shouldn't have caffeine it's better for you not to have it because of the insulin spikes that do occur but everyone is different.
As some people say, "Your milage will vary" Give it a try without it and see how you do.
Best of Luck from the Queen of Caffeine

ChrissyB