Why did they give wine vinegar/sour wine to those who were hung on the cross?
The event that you refer to is recorded in Matthew 27:48.
Immediately one of them ran, and taking a sponge, he filled it with sour wine and put it on a reed, and gave Him a drink.
The Greek word that is translated as “sour wine” is OXOUS. This Greek word refers to cheap, sour wine that was apparently not purchased by the wealthy. It was a “sharp vinegary wine” apparently. It was a common wine that was good to quench one’s thirst. John 19:29 tells us that there was a jar of wine nearby.
A jar full of sour wine was standing there; so they put a sponge full of the sour wine upon a branch of hyssop and brought it up to His mouth. John 19:29 (NAS95S)
The jar of wine was most likely to satisfy the thirst of the soldiers. It seems unlikely that the sour wine was laced with a sedative or a pain killer such as gall, since they had attempted to offer such wine earlier and Jesus had refused it.
And when they came to a place called Golgotha, which means Place of a Skull, they gave Him wine to drink mixed with gall; and after tasting it, He was unwilling to drink. Matt 27:33 (NAS95S)
However, this time Jesus does drink, suggesting that most likely the sour wine was given simply as a drink without anything added. Yet, some have suggested that the sour wine was mixed with gall and was given in fulfillment of Psalm 69:21. But a close examination of that Psalm’s passage reveals that it does not say that the wine contained gall. The reference to gall is in the food. None of the gospel texts indicate that either. However, it is possible that the wine offered earlier might have been the same wine given to Jesus the second time. We cannot know for sure, but is seems unlikely.
Since Jesus was thirsty, He took a brief sip.
After this, Jesus, knowing that all things had already been accomplished, to fulfill the Scripture, said, “I am thirsty.” John 19:28 (NAS95S)
The sour wine was on a long pole. The drink was a hyssop sponge (John 19:29). John Nolland comments,
The third-century B.C. Antigonus Carystus reports the use of sponges tied to poles as a means of bringing up water. So the one who gives the drink to Jesus is not being entirely innovative.
Most likely the sour wine was given as a simple drink for a thirsty dying, suffering man.
1. John Nolland. The Gospel of Matthew. The New International Greek Testament Commentary. Eerdmans Publishing. 2005. p. 1209.