Sync music to a borrowed iPhone without disturbing other content I need to use my daughter's old iPhone 5 as an iPod for a single event (so I can connect it to external speakers via its headphone socket, which my iPhone 7 doesn't have). To do so I need to sync it to my laptop to transfer over the music I need for the event. But it's only the music that I want to sync; I don't want to interfere with any other content on the iPhone 5 — photos, apps (and their data), etc etc I want to leave untouched. Is this possible? 

Oh, and of course she's a teenager so this phone has almost certainly never been synced to a computer (or if it has then not for two years or more) so the idea of 'simply resync it from your daughter's computer afterward to put everything back as it was' is unlikely to be a workable option. And it's not her current phone anyway.
You can't just sync an iPhone to any random computer - even if you are "dad".
Apple's security will just not let you do that.

You would need to release the phone from Find My iPhone, re-set it as your phone, set up as a new device, then you could sync your own iTunes to it.
This would, of course, delete any existing data on it &amp; reassign it as your own device.
You would have to revert that afterwards, using a previously saved backup of your daughter's phone as it was before you 'borrowed it'.

Simpler might be to set up her iTunes on her computer to hold your playlist.
That at least wouldn't require the double transfer of ownership.