The SCANDAL of our Holy God's self-revelation in the written, recorded Word of Scripture and in the living, enfleshed Word Christ Jesus is its very physicalness=humanness=vulnerability and therefore its corruptibility and decayability on every level! And this Word's dynamism includes its ability to address and fulfill each one of each of our needs on every level, including physical, though also, of course, spiritual. Makes me think of the Interpreter's Bible's tawdry habit of over-spiritualizing Jesus' life, mission and teaching!
A whole lot of Jesus' actions and words were sacramental ones – IOW, they pointed away from themselves to a larger essence and reality. The union of the physical with the spiritual: earthiness and the Word of God is part of our definition of 'sacrament;' the sacraments, although mighty acts of God, demand human initiation and participation for their existence! This organic union of physical and spiritual is the reason Protestants always have rejected transubstantiation...as the Methodist Book of Discipline states, that very idea 'overthroweth the nature of a sacrament.'
Mark's and Matthew's accounts of Jesus' 'founding meal' tell of Jesus' predicting his betrayal by 'the one who is dipping bread in the same dish with me.' IOW, a meal can engender the intimacy of community; the betrayal by anyone you've broken bread with is all that more painful since it implies – and means – betrayal of the sacredness of intimacy.
Although I'll probably write more about this later, my answer to Drew is yes, any shared food and drink can be Holy Communion with one another and with our Triune God, but I believe we still need to formally schedule and celebrate Eucharistic celebrations within the context of the gathered people of God, as a reminder of the ongoing sacramentalness of life in Christ; but I also trust the sacraments themselves may be efficacious in ways beyond our more ordinary, day-to-day 'Holy Communions.'