Me: Hey, I'm going to refill my water bottle. You need some as well?
Coworker: Yeah, thanks let me just drink the remaining bits
*starts chugging down 3/4 full bottle*
Me: PFFFFT, you don't need a refill please, for the love of god, staph

I must be lucky to have a co-worker like you

Could land somewhere between "Oh shit, I forgot to drink enough" and "would be nice with some fresh water and I won't expect you to do too much for me"?

Also depends quite a bit on the size of bottle; up to a litre wouldn't seem odd to me...

I very like it, thank for sharing!