I always hate to see questions go unanswered, but I suspect you’re question was difficult to answer. Currently if you purchase the beer mug they will give you a token every time you turn the beer mug in so that you can get the discounted price for your next beer. When I sailed in January no such offer was made to us for a drink of the day. At least one of the five of us have a drink of the day on each day of our seven day cruise.
previously I had brought back my cup to have it refilled but noticed that sometimes I would get a scratchy or colored cup different than what I would actually wish to take home. In one of my pre-Covid cruises it was said my purchase was on file and I didn’t need to bring the cup back. So I’m not going to gas I’m gonna say I don’t know. But with the way they are handling beer using a coin it seems unlikely. If I remember correctly the first one was between 4 to 7 dollars over the next refill cost.