I'm sorry that you're having to deal with it, it can be very distressing & disabling.
I think its risky to assume the driver for your symptoms is the same as mine, there are at least a few quite different reasons these issues happen. In my case interventions for POTS are essential to control my "tolerance" for carbohydrate: if I'm too active in the AM, or if I don't limit the time I spend on my feet, or if I miss medication (Ivabradine & Pyridostigmine) doses, I will struggle again after eating and/or at dawn (alongside a worsening of other POTS symptoms).
With POTS under control I am now able to tolerate a normal amount of carbohydrate and sugar in my diet, but if something disrupts that long-term I would try the Acarbose that was prescribed off-label, or I would go back on a ketogenic diet.
If you're in the UK I'd be happy to share details for the Endocrinologist I saw that helped me with all this