As a child, I went several times (school field trips, girl scouts, and the like) to the Sunbeam Bread factory in New Bedford, MA. At the end of the tour, they’d hand out big plastic drawstring bags full of stuff – toys, like a plastic coin bank, and a ruler with the company logo on it, pencils, and other stuff. But the best part was you always got a full size loaf of bread, still warm, and either a 6-pack of donuts (two plain, two powdered sugar and two cinnamon powdered sugar) or a full size package of english muffins. Good stuff.
We also went a few times to a dairy farm and always got a half pint of milk and a few fun things there, too.
The Cape Cod Potato Chip factory used to let you go through for free. There was a glass wall between the floor where they made the chips and the walkway where the public went through. Don’t know if they still let you in, but that was fun.