The declared service u/s 66E(i) states:
service portion in an activity wherein goods, being food or any other article of human consumption or any drink (whether or not intoxicating) is supplied in any manner as a part of the activity.
Hence, the first and foremost condition here is that there should be an activity which comprises of supplying food or drink along with any other act which tantamounts to execution of a service. It is only on fulfillment of both these conditions that it will amount to a declared service.
As far as sale of items on MRP is concerned, the same should not be subjected to tax based on the D.O.F.No.334/3/2011-TRU