Depending on the nature of what you are trying do and what control you have over the origination of the post request, you may be able to integrate with the Drive API. If the post data can be sent to the user's Drive account as a file (containing raw JSON data for instance), your script could then locate that file, load it's content, do whatever you need with it (put it in a spreadsheet for example), and optionally trash the Drive file. This assumes, of course, that you have control over how the post request is sent. A workflow might involve:
- Client sends post request with data to user's Drive account (tag or name file to be easily identified later)
- Upon completion of Drive File creation, client sends a request to your script with parameter "method=consumeData" or such
- Your script checks the user's Drive account using the DocList service and retrieves any files uploaded for your script
I haven't tried this yet, but should work!