Vintage Good Housekeeping issues had a section where you could as Dr Eddy questions about food, sanitation, and health. This one is from the 1930s:
Q: "Could you tell me what you consider the best time for drinking water?" - J.I.
A: "At one time it was customary to inveigh against drinking water at meals. A series of tests was conducted at Jefferson Medical College in Philadelphia, and it was demonstrated that there is absolutely no harm in this practice provided the water is not drunk for the sake of washing down food that should be chewed before it is swallowed. In other words, the mixing of water with the properly masticated food that we eat is helpful rather than harmful"
"You should drink at least a quart of water a day, and, with the above comment in mind, it will make little difference when that is taken. A large amount of water drunk just before going to bed tends to fill the bladder and may disturb sleep."
I have to say, I had no idea that water was dangerous, or that there was a specific time you were supposed to drink. Good old 1930s, I wish I had worries like this instead of modern troubles.