From the Exomologetarion of St. Nicodemus the Hagiorite:
Canon 69 of the Holy Apostles designates that any hierarch or priest or deacon or subdeacon or reader or chanter who does not fast during Great Lent and Wednesday and Friday is to be deposed. If a layperson does not fast during these times (unless he cannot fast on account of bodily illness), he is to be excommunicated. Do you see how the Apostles numbered the Wednesday and Friday fast together with the fast of Great Lent? Therefore, just as the fast of Great Lent consists in the eating of dry foods, namely, to eat but once a day, at the ninth hour, without consuming oil or wine, likewise, the fast of Wednesday and Friday is to be conducted in the exact same manner. St. Epiphanios also says: "We fast on Wednesday and Friday until the ninth hour." Likewise, Philostorgios says that the fast of Wednesday and Friday does not consist in the abstention from meat, but it designates that one is not to eat any food until the evening. St. Benedict (Canon 41) also designates that the fast of Wednesday and Friday is until the ninth hour. And Balsamon forbids the consumption of shellfish on Wednesday and Friday just as during Great Lent. Let us therefore stop insensibly thinking that the fast of Wednesday and Friday is not an Apostolic directive, for behold, the Apostles in their Canons number this fast together with that of Great Lent... (emphasis mine)
The whole chapter can be found here
St. Nikodemos states quite clearly that days of strict fasting (Wednesdays, Fridays, Lent, etc.) involve total abstinence from food and drink until the 9th Hour (3pm), after which one may eat a single meal consisting of "dry foods" - i.e. vegan - "without consuming oil or wine."
Of course, Scamandrius is quite right when he says you should fast as your Spiritual Father advices you. The above is the rule, not the law.