Vinegar

Concise Bible Dictionary:

This was a thin sour wine, that might be called either wine or vinegar, there being other words for wine of a better quality. It was the drink of the reapers and of the Roman soldiers. It is represented as intoxicating, and as irritating to the teeth. “As vinegar upon niter [natron, an alkali], so is he that singeth songs to a heavy heart” (Prov. 25:2020As he that taketh away a garment in cold weather, and as vinegar upon nitre, so is he that singeth songs to an heavy heart. (Proverbs 25:20)). Its acidity is referred to in Proverbs 10:2626As vinegar to the teeth, and as smoke to the eyes, so is the sluggard to them that send him. (Proverbs 10:26).

From Manners and Customs of the Bible:

Ruth 2:1414And Boaz said unto her, At mealtime come thou hither, and eat of the bread, and dip thy morsel in the vinegar. And she sat beside the reapers: and he reached her parched corn, and she did eat, and was sufficed, and left. (Ruth 2:14). Boaz said unto her, At meal time come thou hither, and eat of the bread, and dip thy morsel in the vinegar. And she sat beside the reapers: and he reached her parched corn, and she did eat, and was sufficed, and left.
1. Chomets—”vinegar”—was a beverage consisting generally of wine or strong drink turned sour. At present it is made in the East by pouring water on grape juice and leaving it to ferment. The Nazarites were forbidden to drink it (Num. 6:33He shall separate himself from wine and strong drink, and shall drink no vinegar of wine, or vinegar of strong drink, neither shall he drink any liquor of grapes, nor eat moist grapes, or dried. (Numbers 6:3)). It was doubtless excessively sour (Prov. 10:2626As vinegar to the teeth, and as smoke to the eyes, so is the sluggard to them that send him. (Proverbs 10:26)). It was similar to the posea of the Romans, which was a thin sour wine, unintoxicating, and used only by the poor. This is what is referred to under the name of vinegar in the narrative of the crucifixion of our Lord. See Matthew 27:34,4834They gave him vinegar to drink mingled with gall: and when he had tasted thereof, he would not drink. (Matthew 27:34)
48And straightway one of them ran, and took a spunge, and filled it with vinegar, and put it on a reed, and gave him to drink. (Matthew 27:48)
; Luke 23:3636And the soldiers also mocked him, coming to him, and offering him vinegar, (Luke 23:36); John 19:29-3029Now there was set a vessel full of vinegar: and they filled a spunge with vinegar, and put it upon hyssop, and put it to his mouth. 30When Jesus therefore had received the vinegar, he said, It is finished: and he bowed his head, and gave up the ghost. (John 19:29‑30).
In Turkey grape juice is boiled from four to five hours, until it is reduced to one fourth the quantity put in. This is called Nardenk. It is of a dark color, has an agreeable sour-sweet taste, is turbid, and not intoxicating. It is sometimes used in the manner in which the chomets is said in the text to be used: the bread is dipped into it. It is thought by some to be the “vinegar” referred to in this passage. (See Bibliotheca Sacra, vol. 5, p. 289.)
2. The “parched corn” is prepared from grains of wheat not yet fully ripe. These are sometimes roasted in a pan or on an iron plate; sometimes the stalks are tied in small bundles, by which the ears are held in a blazing fire until roasted. Grain thus parched may be eaten with bread or without. In Leviticus 23:1414And ye shall eat neither bread, nor parched corn, nor green ears, until the selfsame day that ye have brought an offering unto your God: it shall be a statute for ever throughout your generations in all your dwellings. (Leviticus 23:14), it is classed with bread and with green ears. Jesse sent an ephah of it and ten loaves of bread to his sons in the army, by the hand of David (1 Sam. 17:1717And Jesse said unto David his son, Take now for thy brethren an ephah of this parched corn, and these ten loaves, and run to the camp to thy brethren; (1 Samuel 17:17)). Abigail took five measures of it as part of her present to David (1 Sam. 25:1818Then Abigail made haste, and took two hundred loaves, and two bottles of wine, and five sheep ready dressed, and five measures of parched corn, and an hundred clusters of raisins, and two hundred cakes of figs, and laid them on asses. (1 Samuel 25:18)). David also received it with other provision from the hands of his friends when he was in want, after having fled from his rebellious son Absalom (2 Sam. 17:2828Brought beds, and basons, and earthen vessels, and wheat, and barley, and flour, and parched corn, and beans, and lentiles, and parched pulse, (2 Samuel 17:28)). In Leviticus 2:1414And if thou offer a meat offering of thy firstfruits unto the Lord, thou shalt offer for the meat offering of thy firstfruits green ears of corn dried by the fire, even corn beaten out of full ears. (Leviticus 2:14), it is called “green ears of corn dried by the fire.” It is a common article of food in Palestine and in Egypt to this day.