Go to Settings (gear icon in the lower-right) > Reminders > App reminders
In How many per day?, select the amount and adjust from 0-10 from the list. This adjusts the number of notifications you'd like per day.
You can also adjust for when you'd like to receive Push Notifications in Remind me when? and choose the type you'd prefer under What kind of reminders?
If you are doing this for the first time or did not allow push notifications in the app, a pop up may appear. You will need allow/turn on notifications for the HidrateSpark app within your phone's settings.