I was wondering if anyone else has noticed if the band gets tighter/looser based on your level of hydration?

No

I only noticed cold drinks from the fridge made my band feel tighter

No, but morning is tighter than evening. It's a matter of gravity, with blood evenly distributed in tissues and organs while sleeping, but going to the lower extremities while standing up. Or so I read. Actually makes sense to me since I can see the same thing in my feet.

Same here jwm .....that makes lotsa sense @open/close

Am I am very tight. Coffee only. About 1-3 I begin to get hungry and drink a protein drink. I/2nanana or yogurt. It is evenings I struggle a bit with