Doubt you will find knishes in a supermarket. If you do dont buy them -- they're probably terrible They would have the thick skin and artificial ingredients. If there is a kosher deli there try one before you start your diet,

I need to finish off the bad stuff still in the fridge, before I can start, too much convenience food is mostly not good stuff to be eating
Most of the stuff in the supermarket I go to for the good stuff has a home baked section not a great selection but all freshly made

maybe Home Baked and diabetes don't always mix. I try to think of bread as sugar

Bread is sugar - starch turns into sugar