Can the charging cable of iwatch s7 charge mobile phones?

No.

The battery of the Apple Watch is generally 3v, so the output voltage of the Apple Watch charger should be around 3.3v, and the mobile phone battery is 3.6v to 4.2V. Therefore, it is impossible to charge the mobile phone battery to 4.2v using the Apple Watch charger (output voltage 3.3v), so the mobile phone cannot be charged using the Apple Watch charger. Apple Watch uses sapphire screen and comes in two screen sizes. It supports phone calls, voice reply to text messages, car connection, weather, flight information, map navigation, music playback, heartbeat measurement, step counting and dozens of other functions. It is an all-round health and exercise tracking device. Apple Watch has three series, Apple Watch Sport, Apple Watch and Apple Watch Edition. The three series of watch cases are made of aluminum alloy, stainless steel and gold, and can be combined with a variety of watch straps.