It will be quite challenging. You wouldn't use TTL or JTAG, but the software referred to as MP Tools (Mass Production Tools). You might find the tool for your specific card at somewhere like
http://flashboot.ru/ or
http://www.usbdev.ru/.
Problem is, it is critical to identify the controller in the card, and this is likely been obfuscated to look like something else. Then you need to know the memory chip as well so you can program the controller firmware. There is little documentation, and even if you were to succeed in programming it, I would never trust it for data.
there are a couple of tutorials online for reprogramming fake flash drives, but be careful - there are also quite a few website that host malware and also trojaned flash drive tools around. Common indicators are large blocks of text with a fake clear image over the top, so that clicking to select text or on buttons will result in a redirect, or malware install.