This is really the subject of the entire book - it's not this simple. There are many factors that are involved in someone accepting a truth that goes against what they already know.
"mmm these pineapple chunks for the fridge taste tingly and slightly alcoholic, did you marinate them in sparkling booze or such?"
"probably just fermented a bit, they're five days old"
"hurrrrrrrrrrrrrrrrrrrrrrrrrrrk"
There's much more situations like this, food that fell on the ground, or un(der)cooked meat. People that have a firm basic understanding of how germs work, have some pretty irrational beliefs their ability to teleport to the insides of uncut raw-but-seared-on-the-outside muscle tissue. And many will remain queesy about it, even if you teach them.
My point is, you can lead a horse to water but you can't teach it to fish if it wants to keep warm for the rest of its life.
Though that as a kid, I was educated as to what happens when you drink unclean water or food made at the road side.
There were a lot of educational shows that aired on a channel named Doordarshan. That channel was free and you were able to watch it even without having a cable connection.
The educational/scientific shows aired around 10 AM to 12 PM the time after which most kids started school. So it would happen that I was getting ready for school and learning about all this shit; pun intended.
I never drank water from a shitty source ever again. Never left water in a bucket outside as it leads to creation of mosquitoes etc.
I must admit though, it is not enough. I also remember government officials coming to my grandfather's village where they educated about how mosquitoes are born in stationary water.
I think one of the best thing to do is, give some sort of a portable microscope to these officials, that can let people take the water they drink and observe the microscopic bacteria - or lack thereof - in their water. Even someone who is uneducated or does not know of scientific method will reason with what they see themselves.
Edit: Remove colloquial/useless words and grammar changes.