The watch will only be charged via the supplied cable. Any other cable will result in the immediate voiding of the warranty.
The cable has a proprietary connector for the watch at one end and a standard Typa A USB connector at the other end.
The cable can be plugged in any Type A USB port that provides a voltage of 5V and a minimum current of 200mA. Higher voltages or lower currents may damage the watch as well as the USB port.