No Marriott brand guarantees water.

In practice, 99% of US Marriotts have provided me with bottled water, sometimes (like at FF/CY) on account of status but frequently (like at full service Marriotts or higher end brands) because it's just what the hotel does for everyone. And of course sometimes the water is in the room with a price tag but is free because of status.

No reason not to just ask nicely for waters at check in. Sometimes I ask "are there waters in the room" and the agent says "no but here you go," etc. Sometimes the agent will then offer other items too.

I would not check in on the app if you want the night agent to recognize you, because you might not appear on the "guests still arriving later" list. But I would send a nice note on the chat in the app the morning of arrival like, "Hi, just wanted to let you know I will arrive around 10pm. If you have anything with a little extra space I would appreciate it." I am over 50/50 in getting a response that says something like "no problem" to "we'll secure an suite for you" (versus "upgrades are based on availability at check in," etc.).