She should not be waking up at night to drink. She'll make up for it during the day. It sounds like the sippy cup at night is a comfort item.
She should be drinking regularly. If she's not ready to potty train, then keep her in diapers or pull ups. No other choice. Yes, you have to check kids before you go out, change them if they aren't trained, put them on the potty if they are trained.
I would knock off the juice - it's just sugar and virtually no nutrients.
Why are you checking her blood sugar level? I know excessive thirst is a sign of diabetes, but if you are concerned about this, she should be evaluated by a physician. How is it that you have a blood sugar testing kit for her?
Also, there is a great children's supplement that will nourish her and there is a hydrator which will get the necessary nutrients into her cells instead of being peed out all the time. She's not absorbing all that water - she's peeing it out. If you want more info on better hydration/absorption, I can help you with that.