Keeping water by the bed is more convenient than getting up for a drink, and the bottle prevents spills. If a gf objected to that I would be on OP's side, but clinging to the sucky tube bag even though it annoys his loved one is Sheldon Cooper level. I hope they work it out.

A cup is a great idea. Every morning you can be surprised by what kinds of things float around the air at night, the insects that flew in while you brought in the groceries, heck, if you are lucky, you might even catch a spider or two. Happy sipping!

Plenty of decent folks have 3L+ reusable water bottles.

Why assume I meant nonreusable bottle when it makes much more sense that OP would have a reusable one - if not several, given their interest in hydration? I did in fact mean a reusable water bottle. But I'm probably being overly harsh, because what better way to tell your partner, "I'm someone you can rely on if the going gets tough," than hanging up a plastic water bag with a bite tube?