Why is the Eucharist not an explicit event narrated in the fourth Gospel? Richard Bauckham answers by saying,
I have argued elsewhere that john presupposes that his readers know Mark’s Gospel and deliberately does not repeat what could be read in Mark unless he has a specific reason for doing so. And second, To call Mark 14:22-25 and Matt. 26:26-29 accounts of “the institution of the Eucharist” is misleading because, unlike Luke 22:19 and Paul in 1 Cor. 11:25, they contain no indication that what Jesus does is to be repeated by his disciples. The function of these accounts in Mark and Matthew is to provide readers, in advance of the narrative of Jesus’ death, with a sacrificial interpretation of that death. John has no need of such an account for this purpose, because his narrative of the death of Jesus itself suggests a sacrificial interpretation (John 19:34). So, at the Last Supper he narrates instead another symbolic act of Jesus, the foot-washing (John 13:1-11), which also interprets the death of Jesus, in this case as the culmination of his ministry of loving service in the role of a slave.
Richard Bauckham in his recent collection of essays/lectures, Gospel of Glory, writes about the possibility of the sacraments in the Gospel of John. One of the striking aspects of the fourth gospel is the absence of the sacraments but many theologians and scholars throughout history recognize the presence of sacramental type language throughout. Bauckham argues that John in chapter six is making an allusive reference to the Lord’s Supper to highlight the believer participating in the life of Jesus. He says,
It now becomes clear that eternal life is not just a divine gift to those who believe in Jesus; it is actual participation in Jesus’s own life, made available through his death. This is the significance of John 6:56–57. In verse 57 Jesus explains that he himself lives out of the eternal divine life of his Father, and so believers, participating in Jesus’s life, are alive with this same divine life. In verse 56 he explains that faith in the crucified Jesus unites the believer with him in a union so intimate and enduring that it can be depicted as mutual indwelling and abiding. This language of the reciprocal indwelling of Jesus and the believer is itself, because of its reciprocity, an advance on the language of eating and drinking. John introduces here as a means of connecting this discourse with the Last Supper Discourse, where the image of mutual indwelling recurs (John 10:14–23; 15:4–7) in the context of fuller discussion of the life of discipleship.