I've used Theraband for rehab. They are very similar to using free weights or resistance machines I did not notice any change in BG but I suspect it depends on how many reps and sets you do at a time. The big advantage of them is that you can carry them easily and don't need a dedicated area in the house for them.
I have had dodgy knees for years and took myself off to see a local physio recently. She recommended/supplied them and I do the exercises when necessary. Lots of videos on youtube but I stick to the ones she taught me. I don't think they would have much effect on blood levels.
In my diabetes education class they showed us the resistance bands and had us do some exercises with them, I can't speak for them myself because I'm still young (28) and am now focused on the gym doing strength exercises but a few of the older ladies in my class didn't mind the exercises. Are you able to speak to a physio about this?
I've used them to help strengthen a dodgy shoulder and also for leg exercises. The exercises are gentle and slow (but you know when you've been doing them!) and a lot can be done sitting down, so I wouldn't think they'd raise your BG, @Artville.