Translation:The man drinks a beer before breakfast.
I would say that it changes meaning slightly in English depending on whether the article is included. Without "the" it's a regular breakfast. With "the" it's some kind of event, most likely formal.
So the best translation into English is removing the article, assuming that the definite in Danish here doesn't have the same connotations as it does English and this sentence is about a regular, everyday breakfast.
Usually "en" is added as an article for "the" and is marked as wrong if the article is ignored and not translated or is not used in the translation. Here "morgenmaden" is accepted as "the breakfast" or just "breakfast". I am trying to understand when "the" is required and when it is optional. Can you give any direction?