I think there might be some confusion. Inside the BrewPi Spark is a Particle Photon, not a Raspberry Pi.
The Raspberry Pi needs and SD card and you need to buy one separately. Then you can follow this software install guide to install software (on the Pi) and afterwards connect the BrewPi Spark to the Raspberry Pi via USB for data logging and configuration.
The photon runs the control, the Raspberry Pi runs the Web interface and data logging.
We will release an update to connect the Raspberry Pi and Photon over WiFi later, but this is not available yet.
The BrewPi Spark does have an SD card slot, but it is not used by the firmware. We can perhaps start using it later to buffer data when the connection to the web server is dropped.
The BrewPi Spark is preloaded with firmware, which is in test mode until you configure it differently via the Pi.