<!-- For both Android and IOS -->
<a href="sms:/* phone number here */;?body=/* body text here */">Link</a>
<!-- Use %20 instead of spaces, + for country code -->
<a href="sms:+123456789?body=Question%20from%20me">Send me a SMS</a>
<!-- Without phone number -->
<a href="sms:?&body=Question%20from%20me">Send a SMS</a>