At mealtime, Boaz invited Ruth to dip her bread into what?

Answer: Vinegar

Boaz told her to dip her bread in the vinegar and offered her roasted grain; she ate until satisfied and had some left over.

“At mealtime Boaz said to her, “Come over here; have some bread and dip it into the vinegar sauce.” So she sat down beside the harvesters, and he offered her roasted grain, and she ate and was satisfied and had some left over.”— Ruth 2:14 (BSB)