Flour was ground by stone, tiny pieces of stone made its way into the bread, and the stone stripped the enamel from teeth.
And yes, this was a real thing.
My dad and grandad would laugh at this. 500ml/day is rookie numbers in the former Roman parts of Eastern Europe.
Because they (and many other people) drank more than that, doesn't mean it's a good diet. The Romans drank they wine cut with water though I think.
[0] https://en.wikipedia.org/wiki/List_of_countries_by_alcohol_c...
However, besides the more expensive honey, boiled concentrated grape juice was widely used as a sweetener, for most purposes where today sugar would be used.
Grape juice concentrated and sterilized by boiling has been used for millennia as the main sweetener instead of the more expensive honey, and in most cases the vessels used for boiling must have been made of healthier materials, e.g. bronze in the more ancient times, then cheaper brass during the Roman times.
In the warmer countries of the Middle East, boiled concentrated date juice was used instead of grape juice.