Went to McDonalds and there seems to be some sort of promotion going on with Cedar Fair and McDonalds. I didn't get a large drink, but the cups seem to be valid for a discount at Cedar Fair parks. I saw a KI logo and what I thought was a WWK logo, which makes no sense as Dorney doesn't charge separate admission and the one at Geauga Lake is gone. I'm guessing it was Michigan's Adventure given the similar word lengths.
Edit: Found the press release! https://www.visitkingsisland.com/blog/2018/may/stop-by-mcdonald’s-to-save-usd20-off-admission-to-kings-island
Basically the cup is available at Michigan, Ohio, and Indiana stores and gives you $20 off at KI and CP, and $6 at MA. Those are the prices I thought I saw originally (and why I thought WWK made sense at first).