What does John 19:28 mean?

At many times in the gospel of John, John skips details covered in other writings. Instead, he focuses on personal details not available in those Scriptures. Even at the crucifixion, this pattern continues. John skips over most of Jesus' statements from the cross. So far, he has only included Jesus' command to care for His mother (John 19:26–27). Here, he records another fulfillment of Scripture that comes just before Jesus finally dies.

Gospel writers often point out Old Testament statements which echo in Jesus' life and ministry. John mentioned one of these, Psalm 22:18, when soldiers were gambling for Jesus clothes (John 19:24). Jesus Himself spoke the opening words of Psalm 22 from the cross (Matthew 27:46). Here, John notes a parallel between the suffering described in Psalm 69:21 and what happens to Jesus in this moment (John 19:29). Something that would typically be thought of as disgusting is offered in response to thirst.

"Sour wine" is likely a vinegar. This may be the same or similar to what Jesus refused when He was placed on the cross (Matthew 27:34). If the liquid has numbing properties, Jesus would have rejected it at first, so He would be fully aware and in control during His crucifixion. Now, however, He knows that death is unavoidable and imminent. It's also possible this was presented to Jesus in a teasing, mocking way by His executioners.