K-cup : You will want to read Rav Eitam Henkin z”l’s sefer, לכם יהיה לאכלה, which you can purchase from the publisher, who will mail it to you.
Rav Melamed referred to it in his essay and you will find there a systematic treatment of these issues, with the emphasis on analyzing the sources.
It has multiple haskomos, including from Rav Mazuz.