The facts are that people are not supposed to wake up during the night to go to the bathroom. Our bodies are not made to do that. If they are waking us up during the night to go to the bathroom it is often a sign of a physical illness like Diabetes or something.
When a person starts falling asleep many chemicals come in to play. They paralyze the body so we don't get up and act out our dreams, they regular our bodily organs during the night to fight illness and disease. And at least one chemical tells the Kidneys to stop producing urine at this time.
Our body is supposed to fall asleep and stay asleep for a certain amount of time and not produce urine.
A child does not have these chemicals from birth, they develop during their young life. When the chemical is not present the child falls asleep and they continue to produce urine they have no control over the urinating. It is not anything they can control in any way. This is a developmental stage of the brain that effects the bodily production of urine.
Even kids that do have this chemical can have accidents, they grow and the bladder is not large enough so they wet during the night again after being dry. This is not something they can control very much either. They may not even realize they have to go that much since they have not had this happen before. Suddenly they are wet and didn't even know they had to go yet.
A LOT of kids around 4-5 do this. They have that growth spurt that changes their looks from that of a pre-schooler to a school age child. They just seem to grow from the outside in....
Back to the nights.
If the chemical is not being produced yet it's much like trying to make a 6 month old baby walk independently. They "might" have a time or two that they successfully stand up but it'a a fluke because it's not something they are developmentally supposed to be doing.
So, please understand that there is nothing you can do to make your child produce a chemical to stop urine production during the night. They are doing what they are supposed to be doing. Falling asleep in a deep deep way to where they are fighting off illness and disease and they are dividing cells like crazy and growing continuously.
Buy some night time pull ups and make your life easier. Tell this child they are not going to be dry for a while and this way they can sleep all night. Then stop making your life harder and let this go. When that chemical kicks in you will start seeing a pattern of them waking up dry occasionally then those times will increase. Even when they are staying dry a few nights in a row this does not mean they are done. Accidents truly happen. Keep the pullups for a while longer then you can switch out to underwear.
Drinking water or other fluids has little to do with urine production at night. Actually had a Urologist tell us that limiting their fluids at nighttime was worse due to it not allowing the body to work right. It can cause dehydration and actually make them not be able to hold it even if they are already staying dry.
Don't limit their fluids, let them go to the bathroom before they go to sleep, then put a pull up on them so you don't have to multiply your laundry chores. They will outgrow this at some time in their life. There are very very few people who still wet the bed every night as a normal adult.