Why not "What is in the soap"?
It is accepted, maybe it was added after your question.
Is there any difference in pronounciation of "mít" and "mýt"?
Mýdle or mýdlu: Is there a difference?
Can this refer to a soap opera in Czech? I've seen it shortened to soap in English. But in German you can't shorten it like that, so I wonder if you can in Czech? Are they even called something like "soap operas" in Czech?
No, soap operas are not called by anything like mýdlo. They are telenovely or similar.
It is not true. We use "mydlova opera" as well.