They claim that coming to him is bread, having faith in him is drink. Thus, eating his flesh and blood merely means believing in Christ.
But there is a problem with that interpretation. As Fr. John A. O’Brien explains, “The phrase ‘to eat the flesh and drink the blood,’ when used figuratively among the Jews, as among the Arabs of today, meant to inflict upon a person some serious injury, especially by calumny or by false accusation. To interpret the phrase figuratively then would be to make our Lord promise life everlasting to the culprit for slandering and hating him, which would reduce the whole passage to utter nonsense” (O’Brien, The Faith of Millions, 215). For an example of this use, see Micah 3:3.