Roman glass was not produced on anywhere near sufficient scale and couldn't be.
The most sensible way of safely being your daily liquid requirement was the solution adopted by medieval people. Small beer. 1-2% alcohol doesn't get you drunk but the fermentation does kill almost all germs.
ehhhhhhh that's mostly false. the alcohol in beer like that is not nearly enough to render it safe. It may keep longer, but historically, even in Europe, water has been an incredibly popular drink and if most of it was unsafe and beer was safe, that wouldn't be the case.