Does sin befall one who speaks in the style of the Qur’an in jest, such as saying: "Indeed, to this town do we belong, and to it shall we return," or "No sweets and no coffee except with sugar," without intending to mock the Qur’an?

The first example is what is known as iqtibas (quoting a Quranic verse or Prophetic Hadith and using it out of its original context in one's speech or writing). The scholars differ concerning it; some permit it as long as it is not done in mockery, while others dislike it. It is more prudent to abstain from it. The second example does not present any problem and is permissible speech.