My favorites were touring the Maker’s Mark distillery in the mid 1970’s and JustBorn Candies to see all the steps involved in making marshmallow Peeps. Just Born stopped their tours years ago so I was glad I got to see it.
For anyone living in Pennsylvania, the PCN (PA Cable Network) channel has a program on Sunday afternoons showing factory tours of PA manufacturers. It’s fascinating to see the internal workings of the factories, most not open to the public. The Tastycake one was great.