I am in a different position than you because I am still overweight and a high % body fat but I experienced this when I first started dieting. The sudden loss of caffeine in my life definatly had something to do with it but after doing some research I found I wasn't paying enough attention to how food affects my blood sugar. For me, adding brown rice into one of my meals pretty much made me stable. Until I did that I would have moments where I was really tired, but wanted to try and eat everything in sight at the same time and my leg wouldn't stop bouncing.
Yours most likely has something to do with the thermos also. I have never tried them but read a lot of stuff in miscellaneous forums regarding some of the side effects people have experienced. I think most of them always mentioned sweating so you can probably do a forum search with "thermorexin" and "sweating" as the keywords and find most of them.
edit: Also, when I first started dieting and exercising my resting heartrate halfway through the day averaged 67 bpm (I'm a pretty calm person). After just a little bit of time it has jumped to average 75 bpm mid day. Although it doesn't seem like a big difference by the numbers, the physical effect on me in the beginning definatly made me feel "hyper" at some points during the day. It may be totally unrelated to my heart rate but it seems easier to focus on things like homework until they are done as well.