Pliny the Elder described sugar, but he said that it was used only for medicinal purposes, presumably because having to be imported from India through Arabia it was available only in small quantities and at high prices.

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.

Oh wow, why did I think sugarcane is a New World crop? Apparently from Papua.

They had a very toxic replacement though, basically grape juice sirup rendered down in lead kettles.

Indeed, lead acetate is an artificial sweetener.

While some had indeed the very bad idea of using lead vessels for boiling the juice, both because lead vessels were cheaper and because that might have enhanced the sweetness, due to the taste of lead acetate, it is unlikely that this was a widespread practice.

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.