Google Glass v1 (and v2) is capable of playing audio through the micro-USB connector that is used to charge the device.
To make your own earphones for Google Glass, you will need either 1 or 2 earphones, a 500K Ohm resistor, and a 5 pin micro-USB connector. I did not have a 500K Ohm resistor available, and used a 470K Ohm instead. It seems to do the job without any problems.
With the connector laying down, and the 2 pins facing upward, the pinout is as follows:
Connect the resistor to pins 4 and 5.
Cut the wires from your existing earphones as long as you need them to be.
If you are using a single earphone (mono), you should bridge pins 2 and 3. With mine, I used part of the lead that I cut from the resistor. Connect the positive wire from the earphone to pin 2, and the ground to pin 5.
If you are using two earphones (stereo), connect the wire from the left earphone to pin 2, and the right earphone to pin 3. The ground wire should connect to pin 5.
Note that pin 1 is not used.
This is the micro-USB connector with pins 1, 3, and 5 facing upward.
Verify your work, and check for shorts or bare wires touching.
Close up the micro-USB connector, and you are ready to use your earphones. You can probably fill the connector with epoxy to ensure that if a wire were to loosen, that it will not short.
This is the finished micro-USB connected to my Glass.
DISCLAIMER: I can not be held responsible if you do this wrong, or if your device gets damaged.