Yeah its not really crucial, or really necessary since water will have fluoride in it now anyway (depends where you live). It helps a bit but as long as youre brushing and flossing enough you'll be fine.

Flossing is more important than brushing. The most common and likely place for enamel loss and then teeth erosion/rot is the sides and under the gum slightly as this is where all the gunk builds up. Like a keyboard, the individual keys might be dirty, but the spaces between them will always be worse. Id reccomend flossing after every meal than not drinking after brushing.

Also, brush your gums. Circular motions as to prevent erosion. Mouthwash is pretty much a scam. And dont ignore behind your teeth.