How can we get subscriptions data for orders via API?

You can retrieve subscriptions data through our Seal Subscriptions Merchant API. You can even set up webhooks to get notified when a subscription is created or updated in your shop. 
You can view the documentation for the API here: https://www.sealsubscriptions.com/articles/merchant-api-documentation 
We also prepared a sample API client here: https://github.com/SealSubscriptions/Seal-Subscriptions-php-API-client