It's still the sugar equivalent of having a small cup of tea/coffee/water, and stirring in 4 sugars. If chugged down quickly, that's quite a hit! Even if not, it's still more sugar rich than most things you'll intake in your day-to-day.
Your experience may well be due in part or whole to taurine, I can't say. But parents of young children everywhere can attest to the effect of one overly sugary serving resulting in quite a bit of resultant hyperactivity and mood change over the following hours. So your experiments may benefit from some controls in that respect.
Note that energy drinks have caffeine, and if you consume a lot of caffeine in a short time it can be fatal.
For anyone wanting to consume taurine, you can simply buy taurine. No need to drink energy drinks which I'm sure aren't super healthy (even without sugar).
I drank an energy drink recently (a couple weeks ago) after many years of avoiding it. Simply drinking 1/3rd of a 16oz monster shifted my mood. I became instantly happy and was humming songs like I used to pre-depression. This lasted throughout the day.
Pretty anecdotal, but I think it is the taurine in the drink. Just Coffee/Caffeine does not have this effect on me. To ascertain the effect of taurine, my next step is to start my day on 1g of Taurine from Life Extensions taken on an empty stomach as advised on the nets. Fingers crossed.
Just wanted to share my experience for serendipity.