The last of these situations happened one Sunday when we had a lesson about fasting. One brother that occasionally attends became very offended about the whole topic. The instructor had explained right up front that those that have special health needs (which would include this brother) should not risk their health by abstaining from food and/or fluids. But for some reason that disclaimer wasn't enough. The man felt that he was being judged simply because of his health condition.
Once things settled down, a new point of contention arose over whether it is acceptable to drink water during a fast. After all, if the purpose of the fast is to give to the needy the value of that which would otherwise have been consumed, and the monthly water bill is unaffected by a few cups of water, why is it necessary to be dehydrated? Isn't the "drink" referred to in the proscription on drink during a fast (see Handbook #2 section 21.1.17) something for which you would pay, such as soda pop?
I'm sorry to say that our group waxed rather Pharisaical on this point. There was much bickering. The mormon.org website (scroll down and click on OBSERVE THE LAW OF THE FAST) clearly states, "Once a month, God asks us to fast, or forego food and water for two meals." But as I understand it, the website does not claim that its content constitutes actual church doctrine or policy (except where directly quoted from authoritative sources).
Russell M. Nelson wrote an answer to the water during fasting question when he was the General Sunday School President in 1976, saying about abstaining from drink that "the use of water is excluded in this kind of a fast." But right up front the article clearly states, "Questions of general gospel interest answered for guidance, not as official statements of Church policy."
The First Presidency under Heber J. Grant issued an official statement on this topic in 1932 saying:
"When fasting, members of the Church are advised to abstain from two meals each Fast Day and to contribute as a donation the amount saved thereby for the support of the worthy poor; also by prayer in connection with fasting to develop spiritual power. No direct instruction is given in the Doctrine and Covenants regarding abstaining from water while fasting. In the Bible there are three references in connection with fasting and abstaining from water. These are: Exodus 34:28 and Deuteronomy 9:9-18, where it states that Moses 'did neither eat bread nor drink water'; and Esther 4:16, where Esther asked the Jews to fast for her and to 'neither eat nor drink.'
"The spirit of fasting is the main thing to encourage. Too much stress should not be laid on technical details, but the self denial of food, striving for spiritual strength and donating for the benefit of the poor should constantly be in mind."This statement sounds very non-committal to me. It's kind of like, "If you want to go without water while fasting, go ahead. But don't get too tied up in the details. It's mostly about not eating food, praying, and caring for the poor."
By the time our group got around to people trotting out various evidences to support their points of view on the matter, I think it's pretty safe to say that we had gone far afield from the spirit of the law and were debating the letter of the law. Wasn't that kind of behavior repeatedly condemned by the Savior in the New Testament?
But none of this answers the question of whether your fast is acceptable if you drink water on fast Sunday. I'm afraid that my answer on this point resembles what I say when a child of mine mopes around on fast Sunday asking if he can eat yet: "Well, the family is ending its fast at such-and-such time. If you want to end your fast earlier, that's between you and the Lord. You talk it over with him and do what the Spirit tells you."
Yes, that's a guilt trip wrapped up in the soft shell of a righteous sounding answer. But it puts the responsibility where it belongs. Most of the time my children decide to endure, but not always. I don't nag or berate the child about his choice. After all, maybe the child's fast was acceptable. At any rate, the Lord blesses the child according to the faith applied.
My advice is similar when it comes to drinking water while fasting: it's between you and the Lord. Do what the Spirit tells you is the right thing for you. And don't get all hot and bothered about how others choose to observe the fast.
Let me tack a disclaimer onto that advice. You should take anything I say on this matter with a grain of salt. Or not. Salt would only make you thirstier.