4 Or “Supper.” To avoid possible confusion because of different regional English usage regarding the distinction between “dinner” and “supper” as an evening meal, the translation simply refers to “the evening meal.”
5 At this point the devil had already put into the heart of Judas Iscariot, Simon’s son, that he should betray Jesus. C. K. Barrett (St. John, 365) thought this was a reference to the idea entering the devil’s own heart, but this does not seem likely. It is more probable that Judas’ heart is meant, since the use of the Greek article (rather than a possessive pronoun) is a typical idiom when a part of one’s own body is indicated. Judas’ name is withheld until the end of the sentence for dramatic effect (emphasis). This action must be read in light of 13:27, and appears to refer to a preliminary idea or plan.
6 Or “that he should hand over.”
7 Grk “betray him”; the referent (Jesus) has been specified in the translation for clarity.

In other versions

During supper, when the devil had already put it into the heart of Judas Iscariot, Simon’s son, to betray him,

The evening meal was in progress, and the devil had already prompted Judas, the son of Simon Iscariot, to betray Jesus.

Now when it was time for supper, the devil had already put it into the heart of Judas, Simon Iscariot’s son, to betray him.

It was time for supper, and the devil had already prompted Judas, son of Simon Iscariot, to betray Jesus.

And as a dinner was taking place, when the devil had already put into the heart of Judas son of Simon Iscariot that he should betray him,

And supper being ended, the devil having now put into the heart of Judas Iscariot, Simon’s son, to betray him;

Public Domain