Re: Man, this is rough!
It sounds just like how I feel when I get low blood sugar during pregnancy. I get it at other times, too, but much more often when pregnant. And for some reason, it tends to hit me hard when I'm just standing around - like waiting in a check-out line or something like that. I would have been fine walking around the store, stand in line for a few seconds, and *bam* it hits me.
I have had to sit down on the floor before, to prevent myself from passing out. Overall, even without the anxiety of making a fool of myself by fainting, it just feels really crappy. And a really bad low (when I don't get something to eat to help right away) can leave me feeling off for the rest of the day.
And yes that is why you felt better after drinking soda - but please don't let that be your "go to" for preventing it! When you drank it, you got a bunch of sugar - this is good as it gets rid of the low blood sugar. But without having protein to make the sugar "last" in your system, you'll be feeling crappy again rather quickly. If I only get sugar into me, it will last my body maybe half an hour, then I get low again.
The best thing I've found to help is some trail mix - the one I like has craisens and raisens (giving me a quick sugar boost), and also has a bunch of different nuts (protein to get things regulated for a while). If I get feeling low at all (you'll get used to recognizing it before it gets bad) I just grab a bag of the mix and eat it - I always keep a couple in my diaper bag or purse, just in case.
Granola bars would be good, too. And there is a special "bar" for diabetics that works really well - but they are really sweet and kinda $$.
Definitely make sure you're staying hydrated - lots of water. But try not to rely on the soda as your "rescue", it's really a short term solution.