The drinking water thing is so stupid. Autistic people tend to have lower bodily awareness than typical people and/or difficulty filtering what sensations mean.
We all come to the world only feeling "okay" or "not okay" and we learn to interpret these signals as hunger, loneliness, whatever. I'm sure some people here have realised they eat when they're actually bored or sad. Autistic people are less good at this in general than typical people.
They do not actually need to be reminded to drink water or they'll die of thirst. That's not a thing. Eventually that thirst feeling, or hunger, gets through. Also, human beings do not need to drink water at two-hour intervals, and I don't care whether everyone carries water everywhere now; People were not collapsing everywhere of dehydration in the nineties and we didn't do that then.
And do you know what an actual autistic person would do if he felt he wasn't drinking enough water? Set up an autistic system and keep to it even when it was annoying or inconvenient for the people around him, or else feel distress that the Water Drinking Schedule was not adhered to.