The Bellabeat app will only give you tailored hydration advice if you use the Spring.
In case you wish to set up hydration reminders, you can do that even without owning Spring.
In order to set them up drinking reminders, you can do that by clicking on the Hydration feature on the main dashboard of the Bellabeat app and set the reminder for an ideal time interval for you.
You can learn more about the hydration reminders and how to set them up in this article.