Adam Clarke on Ruth 2:14

Dip thy morsel in the vinegar - The חמץ chomets, which we here translate vinegar, seems to have been some refreshing kind of acid sauce used by the reapers to dip their bread in, which both cooled and refreshed them. Vinegar, rob of fruits, etc., are used for this purpose in the East to the present day; and the custom of the Arabs, according to Dr. Shaw, is to dip the bread and hand together into these cooling and refreshing articles.

Parched corn - This was a frequent repast among the ancients in almost all countries; see the notes on Lev 2:1-14 (note).