Client: Google analytics is saying our bounce rate is 86%, Could you fix what you did to improve this?

It's a single page website -.-

86 on single page website, they should receive a reward 😂😂😂😂

Actually, you CAN fix it, just add this at the bottom of the single page:
<script>
setTimeout(function() {
ga('send', 'event', 'time', '20s+');
}, 20000);
</script>
It sends an event to Google Analytics, which is like the user clicked to go to another page, so it will affect the bounce rate, like with regular websites. I set it to happen after the user spends 20 seconds on the page (hence not closing it after a few seconds and going away), and you can adjust that value. But you can also set it to happen on some other event on the single page, like clicking on a button or navigation links, or some other action, if you have one. Cheers :)

the bounce is also related to the time spent within the page or any cta that you declare and it's executed (contact form for example)

it's kind of arbitrary, but I believe (without evidence) that above one minute is not a bounce.

I do think is more a matter of content than code.

I don't get it.. ? You can implement ga to work with spas