Translation:When will you have taken your medicine tomorrow?
So basically like how a Dane would say it in Danish.
I probably shouldn't have written that it is grammatically wrong in Danish, but it's very constructed and you would never hear it or even see a Dane write it.
In English it sounds a bit posh, though.
"When will you have taken your medicine tomorrow, sir?" - Some Butler
The only reasonable use this sentence would be a reply to a statement like "I'll clean my room after I've taken my medicine tomorrow!" Then it's reasonable, if a bit odd, to use the future perfect to ask a question in response.
Awkward sentence all around though, not a good example.