Hi @Heavy,
Good question! There was a thread on this subject, and they came up with an example script that pulls data by running some javascript on Google Docs to pull data from the core:
(this script: Spark to google spreadsheet - Pastebin.com)
There have also been some good threads on sending http POST and GET requests, here's my goofy http get wrapper with basic auth: Doorbell to send jsonrpc - Getting Started - Particle -- It's possible your POST request is failing for a lack of cookies and auth headers, but I'm not super familiar with the security requirements of posting to Google Docs
Thanks,
David