When Jesus had RECEIVED the sour wine, he said, “It is finished,”

[TonyChanYT]

NASB 1977, Psalm 69:

21 They also gave me gall for my food, And for my thirst they gave me vinegar to drink.

How did Jesus fulfill the above?

It is a bit puzzling/tricky.

At the beginning of the crucifixion, Mark 15:

23 they offered him wine [G3631] mixed with myrrh, but he did not take it.

Matthew offered a bit more detail, 27:

34 they offered him wine [G3631] to drink, mixed with gall, but when he tasted it, he would not drink it.

It was a mixed or drugged wine to numb the senses. Jesus detected the gall/myrrh and refused it so that he could keep clear-minded on the cross. At the Last Supper, Jesus promised not to drink G3631-wine until the future kingdom.

Some hours later, ESV, Luke 23:

36 The soldiers also mocked him, coming up and offering him sour wine [G3690].

NIV called it wine vinegar. This was a different Greek word for a different kind of wine. This was the ordinary sour wine to quench thirst. Jesus probably refused to drink this time also. It was not the right now.

However, near the end of the crucifixion, Matthew 27:

47 some of the bystanders, hearing it, said, “This man is calling Elijah.” 48 And one of them at once ran and took a sponge, filled it with sour wine [G3690], and put it on a reed and gave it to him to drink.

Mark 15:

36 And someone ran and filled a sponge with sour wine [G3690], put it on a reed and gave it to him to drink, saying, “Wait, let us see whether Elijah will come to take him down.” 37 And Jesus uttered a loud cry and breathed his last.

John was more clear, 19:

28 After this, Jesus, knowing that all was now finished, said (to fulfill the Scripture), “I thirst.” 29 A jar full of sour wine [G3690] stood there, so they put a sponge full of the sour wine on a hyssop branch and held it to his mouth. 30 When Jesus had received the sour wine, he said, “It is finished,” and he bowed his head and gave up his spirit.

Ellicott:

This vessel of the ordinary sour wine drunk by the Roman soldiers, was placed near in order to be given to those who were crucified. Thirst was always an accompaniment of death by crucifixion.

From some bystander's offering, Jesus took just enough liquid [G3690-sour-wine] to water his mouth and throat so that he could utter his final words with a loud cry: "It is finished."

How did Jesus fulfill Psalm 69:21 at the crucifixion?

Initially, he refused the gall-wine [G3631]. In the end, when he accepted some regular vinegar wine [G3690], he died right away. It was fulfilled, done, and finished.