Feel jittery and nauseas after drinking a sugary drink-24.5 weeks preg?

I drink water/milk/juice throughout the day but I usually give myself a break around lunchtime. I usually drink a coke or sweet tea because the caffeine and sugar help my headaches and give me that pick-me-up I need. The past 3 weeks or so, I've noticed even drinking half of a coke or tea, I get really jittery, nauseas, and a rapid heartrate. I mentioned it to my doctor 2 weeks ago and he said just wait until my sugar test, which will be in about a month. Of course, it's common sense to not drink anything sugary anymore but I'm wondering is that normal for me to feel that way while pregnant? Up until a few weeks ago, I could drink 2-3 cokes or teas a day and feel fine. Btw, he did test me for anemia a month ago and it was only minor anemia and I started an iron pill. The weakness and dizziness I had then has gone away, so I'm thinking it's not from being anemic anymore.