Why is wine associated with St John the Apostle? In the Rituale Romanum of the Catholic Church one can find a blessing for wine which is reserved for the Feast of St John the Apostle (December 27).

Why does the Catholic Church associate this tradition with St John?

Occasionally artists show a snake or a dragon coming out of a chalice with St. John the Apostle.



El Greco: St. John the Evangelist, 1595-1604
The reason is:


  The Church provided a special blessing of wine in honor of the Saint.
  According to legend St. John drank a glass of poisoned wine without
  suffering harm because he had blessed it before he drank. The wine is
  also a symbol of the great love of Christ that filled St. John's heart
  with loyalty, courage and enthusiasm for his Master; he alone of all
  the apostles was not afraid to stay close to Our Lord during the
  Passion and Crucifixion.


This is the source

So tradition say:


  St. John’s wine, blessed by a priest or sprinkled with holy water by
  the father of the family, is served with the main meal. In Europe,
  even the children receive a little sip of it after the main course of
  the dinner. The wine is then poured into glasses and passed around to
  the family and guests. As each glass is given, the leader says:  “I
  drink thee the love of St. John.”
  
  The response to this is:  “I thank thee for the love of St. John.”


This is the source