Butler County started its Donut Trail in January 2016. It consists of eight family-owned bakeries, each with its own specialty, who sell their wares to drivers making the rounds.
Before you start, you print out a passport with the bakeries listed. There are 10 listed, but I believe the one in Oxford is closed now and that listing is already stamped on the passport. Another bakery has two locations and you need to visit only one or the other. Once you get all the locations' stamps you can send your completed form to Butler County and in return you get a free T-shirt.
You can't visit all the bakeries in one morning unless you start about 5 a.m. Believe it or not, some of these places open at 2 a.m.! Some friends and I split the trip--we went to five places on the Saturday before Memorial Day and the other four on the Saturday before Labor Day. Another reason you can't complete the tour in one day is that most of these places close by noon, if not before, when they run out of baked goods.
You can buy not just doughnuts, but also other pastries and even cookies. We'd eat our first purchases in the car, but save the remainder for the rest of the weekend. One friend did eat all of her purchases that first morning and by lunchtime was rather bloated.
Here is the link for the Donut Trail:
And this is what the shirt looks like: