How do I force audio out through lightning to a USB connection?

Just switched from an iPhone 6 which has a stereo-out jack to an iPhone X that does not. I had used the audio jack to connect to my car stereo and another USB to power the phone. Now that there's no audio out, I can only directly plug the usb cable directly from the phone to my car, but my car doesn't recognize the phone as a USB storage device since I don't have any songs loaded onto it yet. How do I force the audio to go out through the USB like it was a dock connector so I can listen to podcasts and streaming audio? When I tap the audio-out icon, the list doesn't include USB / dock connector out.