I'm not sure if it was a legacy Marriott thing or not. There have been a few times that I've been offered water at check in (Residence Inn tends to give out a small bag of stuff due to status) but most of the time, when I've gotten it, it's because there are some bottles that came with the room and are replenished by housekeeping. I don't think that had anything to do with status because it has happened regardless of whether or not I was upgraded. I've also grabbed it from the Concierge Lounge when there was one that was open.

As I mentioned in another post, most often, I just hang on to an empty water bottle, sometimes I bring a personal water bottle, and refill it in the fitness center.