While I ordered up and use a Freedompop sim card for free, I did pay 13 bucks for the card. It's given my iPhone 5s 200 megabytes of internet a month, 100 minutes of calling and 100 SMS texts for no monthly fee. That's enough to use an app and the phone without a monthly charge.
That's as close to free as I've found.
How to make internet sim card for free?