My manager told me I cannot move my water around.

This is primarily a Boomer thing. For some reason, Boomers — especially Boomer women — expect to experience all retail employees in a state of mute obedience, with no observable human needs or limitations. They must not sit. They must not drink. They must accept all abuse with a smile.

Why Boomer women? My guess is that they are in unhappy marriages with uncaring and uncontrollable men and this is the one area that they can exert some measure of power. Sadly, by bullying 17-year-old grocery store checkers.