"when i wake up in the morning, i eat breakfast; as soon as i arrive at work, i eat a doughnut; along about 10:30, i take a break and eat brunch; at noon, i eat lunch; on my afternoon break, i eat something from the vending machine; when i arrive home, i eat supper; and guess what i do before i go to bed?"
"do you... do you..."
"go on: ask; i know you want to."
"do you eat again?" [<------<<< there it is.]
"no: i brush my teeth."
Would that sentence make any sense to an English-speaking person? I haven't a clue as to its meaning and nor has anyone else I have asked. From my point of view, I feel the vocabulary and the grammatical points would be more easily understood if the sentences were more coherent.
That's misleading. If you google with quotation marks surrounding it (to look specifically for that phrase, as opposed to the individual words), you only get 16 results. Googling the Irish sentence "An itheann tú arís" yields even fewer results: 1 (this very page). On the other hand, the present progressive equivalents, "Are you eating again" and "An bhfuil tú ag ithe arís" yield, respectively, 19,800 and 40,500 results. So although I understand the point of using this sentence to illustrate the usage of an adverb, it may be doing more harm than good to introduce it in this way -- learners of Irish may think that this is the way to ask "Are you eating again," when in fact Irish speakers also use the present progressive. Duolingo should introduce this form earlier: Rosetta Stone introduces it almost from the very start.