Note that v1 is no longer being updated, and that v2 doesn't use a Sync Token. Learn more.
You can get a sync token via one of the options below:
You can use a Cloud Service Provider like IBM Cloudant.
You can also setup your own hosting or setup CouchDB on your computer with Bitnami.
After you get either done, you create a DB (any name works) and then the
Sync Token is the full DB URL with username and password, like https://user:pass@hostname/dbname
(no trailing slash!).