Dan 10:1-3 In the third year of Cyrus king of Persia a message was revealed to Daniel, whose name was called Belteshazzar. The message was true, but the appointed time was long; and he understood the message, and had understanding of the vision. In those days I, Daniel, was mourning three full weeks. I ate no pleasant food, no meat or wine came into my mouth, nor did I anoint myself at all, till three whole weeks were fulfilled.
Daniel fasted 3 weeks without food and drink (including water). Moses fasted 40 days up in Mount Sinai without food and water. Similarly our Lord Jesus Christ fasted forty days in the wilderness without food and water.
Fasting means no food nor drink (including water) for the whole period of fast. Surprisingly, so-called servants of God are teaching Christians dieting instead of fasting ( i.e taking juices or fruits or reducing the meals). Dieting is not fasting. Human diet mainly for reasons of health or beauty.
Brethren do not deceive yourself that you are fasting (holy, holy) when you are actually dieting for your personal benefit.
Isa 58:3-5 'Why have we fasted,' they say, 'and You have not seen? Why have we afflicted our souls, and You take no notice?' "In fact, in the day of your fast you find pleasure, and exploit all your laborers. Indeed you fast for strife and debate, and to strike with the fist of wickedness. You will not fast as you do this day, to make your voice heard on high. Is it a fast that I have chosen, a day for a man to afflict his soul? Is it to bow down his head like a bulrush, and to spread out sackcloth and ashes? Would you call this a fast, and an acceptable day to the Lord?
Isa 58:6-8 "Is this not the fast that I have chosen: To loose the bonds of wickedness, to undo the heavy burdens, to let the oppressed go free, and that you break every yoke? Is it not to share your bread with the hungry, and that you bring to your house the poor who are cast out; when you see the naked, that you cover him, and not hide yourself from your own flesh? Then your light shall break forth like the morning, your healing shall spring forth speedily, and your righteousness shall go before you; the glory of the Lord shall be your rear guard.
Fasting is to afflict oneself so that we experience the sufferings of the hungry poor and needy. It also helps to make us more merciful and compassionate.
Dan 10:5,12 I lifted my eyes and looked, and behold, a certain man clothed in linen, whose waist was girded with gold of Uphaz!.. And he said to me, "O Daniel, man greatly beloved, understand the words that I speak to you, and stand upright, for I have now been sent to you." While he was speaking this word to me, I stood trembling. Then he said to me, "Do not fear, Daniel, for from the first day that you set your heart to understand, and to humble yourself before your God, your words were heard; and I have come because of your words.
After the fasting of Daniel, God sent the angel to Daniel addressing him as the man greatly beloved of God and also showed him a vision.
I believe that if our sincere and humble fastings are pleasing to Him, we will see His presence with the manifestations of signs and wonders: - enlightenments, healings, deliverance, understandings, truth, etc.
Dan 10:14 Now I have come to make you understand what will happen to your people in the latter days, for the vision refers to many days yet to come. "