How often does data sync from Health Connect?

You can change the frequency from the settings. In Exist for Android, tap the ⚙ cog icon to open Settings, then tap "Health Connect attributes".

The default frequency is syncing every hour, but this can be changed up to the longest period of 4 hours.

Please note that even at the most frequent syncing of every one hour, some attributes will not sync this often, to conserve your battery. For example, sleep changes will only sync every 4 hours once your sleep has first synced for the day.