GET https://www.patreon.com/api/oauth2/v2/campaigns/${ID}/members?include=user&fields[user]=email
This response without email.
GET https://www.patreon.com/api/oauth2/v2/campaigns/${ID}/members?include=user&fields[user]=email
This response without email.
You would need to request the proper scope when authorizing users via your login process, then you can ask for the email with the resulting token.