Do you mean for labour?
I also had gestational diabetes and ate normally the day of birth. I noticed I was getting more and more of low blood sugar episodes which made me feel like I had to faint. Nearing birth your placenta starts to deteriorate and it has less and less of an influence on your hormones. But I never had high readings. Never even had a peak after I started testing my blood, I think I was a false positive.
Do you have to test yourself?x
With getting induced they may suggest to avoid snacking - especially if you’re on the drip/have an epidural. Depending on how well controlled your GD has been, some trusts will run a sliding scale dextrose infusion during labour.
anyway, to answer your original question: nuts, berries, you could make your own coconut/dark chocolate bars. Greek yoghurt, full fat is good but not much use without a fridge lol!