Language can be a historian. A reminder of this was hearing a Spanish boy use his word for sugar: azúkar. That reveals its origin: originally the Arabic al-zukar, which is a reminder that sugar refining came into Europe from Arabia and other parts of the Levant.
Refined sugar as a commodity seems to have been commonplace by the time of Shakespeare, who mentions it repeatedly; and it is mentioned as early as 1299 in the accounts of the Abbey at Durham. But the people of ancient Greece and Rome were not acquainted with it.
Its existence however was known to Pliny the Elder, who mentions it in the Naturalis Historia, XII.17. This is a passage in one of the books that deal with matters botanical, and he mentions sugar along with the herbs and spices produced in the East:
Saccaron et Arabia fert, sed laudatius India. est autem mel in harundinibus collectum, cummium modo candidum, dentibus fragile, amplissimum nucis abellanae magnitudine, ad medicinae tantum usum.
¶ Arabia also produces sugar, but that of India is more prized. It is a honey collected in reeds, white like gum, and brittle to the teeth, the largest amount the size of a hazel nut—used only for medicine.
The Greeks and Romans of his time may not have been acquainted with it, but it was certainly part of their diet: not just in honey and figs (which can be more than 50% sugar) but in any fruit and indeed in lesser amounts in vegetables; and by metabolism in wine and any other drink containing alcohol, which the body converts to sugar.
All this may be corrective if students are being zealously given to understand that sugar is in itself a poison—and they may need to be acquainted with the view of Paracelsus:
Omnia venenum sunt: nec sine veneno quicquam existit. Dosis sola facit, ut venenum non fit.— Defensio III, 1538
Which is sometimes paraphrased as ‘Every medicine is a poison, and every poison a medicine.’