yes fasting can have benefits, but the way most Muslims do it (in summer specifically) actually hurts. your body needs a minimum amount of water and salt to work properly throughout the day.
But remember that this fast is done for mental reasons, and not physique. Even though it can be difficult, I really look forward to it throughout the year. It does bring euphoria and increased focus and other positive "mental" effects.
To say it has no benefits is obviously wrong. It can be a great experience!
Think about it, you don't drink while sleeping, so that's 7 or 8 hours right there. If you ever been not drinking for 2 or 3 hours before going to bed, than you're close to 12 hours.
In fact, google "dry fasting", lots of people are experimenting with it. "dry fasting" for 24 hours feels very different than "water fasting" for the same amount of time. There is no published scientific studies about it, I suspect because of liabilities fear when people go to extremes, but I am convinced that short term (~ 24 hours) it is different and beneficial. Every theory you will find online is bro science, but, you can't dismiss hundreds (thousands) of people experimenting and and reporting positive results.
I fast for 23 hours every day, eating one larger than normal meal in the evenings.