I’m T2 diet only and risking cross posting but I was very similar, thirsty after meals and a bit tired but BG well within range, I was drinking small glass of sugar free Irn Bru only with meals (one of my few vices) didn’t have it for a few days and noticed the thirst wasn’t happening and I had more energy. So tried going back to it and it happened again.
It may not be this but I put it down to the sweeteners in the pop not affecting my BG at all but causing the other problems, I’ve stopped drinking it now and it doesn’t happen anymore