Question:
Answer:
The Church’s rule for fasting before communion is very clear:
A person who is to receive the Most Holy Eucharist is to abstain for at least one hour before holy communion from any food and drink, except for only water and medicine. (canon 919 §1)
The Church’s rule of fasting at other times is fairly vague:
The law of fasting allows only one full meal a day, but does not prohibit taking some food in the morning and evening, observing—as far as quantity and quality are concerned—approved local custom. (Paenitemini, Pope Paul VI)
Fasting before communion rules out all beverages besides water. When fasting at other times (e.g. Fridays in Lent) the Church does not explicitly forbid any kind of beverage so coffee or soda would be permissible. Obviously meal replacement drinks would fall under food rather than beverages.