Sounds like your teeth lack fluoride

the water here is thankfully unfluorinated.

i also brush with a toothpaste containing fluoride and have a healthy diet.

>I’m more confused by how you would coat your teeth while drinking, do you swish it around in your mouth every sip?

I mean we are really going down a rabbit hole, but the water goes in my mouth, I swallow, my mouth remains wet with some residual water.

Unless you're opening your throat and pouring directly in, I guarantee water is touching your teeth, even with a straw.

that sounds like a terribly inefficient way to get fluoride on teeth compared to toothpaste