Bakeries are sold when people get enough cupcakes, and when production/advancement is very slow. Generally, people first sell between 2,000 and 10,000 cupcakes(depending on money spent on the game). When selling your bakery, you will keep

  1. All past cupcakes earned
  2. Premium upgrades
  3. All rainbow cookies
  4. All cupcake upgrades
  5. All super structures
  6. All super cookies
  7. Rainbow cookies in your magical tip jar
  8. Themes
  9. Milk
  10. Achievements
  11. Stats
  12. Cookie mastery
  13. Secrets
  14. Golden structures
  15. Golden super structures
  16. Golden super cookies
  17. Daily gifts
  18. Loot Bags collected for that day
  19. Bakeries, and Bakery level
  20. Boost tokens
  21. Showcase items
  22. Cookies collected
  23. Hidden words solved

What you will NOT keep

  1. Upgrades
  2. Structures
  3. Structure upgrades
  4. Cookies(bought from the cookie tab)
  5. Cookie set upgrades
  6. CPS

Of course, that's all easy to get back.

That is all for now if I forgot something please tell me :D