There seems to be a fundamental lack of understanding here so I'll provide a short answer and a longer one.
short
You can not send dynamic variables to Sass. There may be some port of it for PHP that makes it possible but using just Sass, this isn't feasible.
longer
You may want to familiarize yourself with what exactly Sass is and how it fits in to your toolkit. It sounds like you're using PHP so I imagine you'd have PHP rendering out HTML templates/doing DB magic, maybe a dash of JavaScript to do client side scripting, and you'll have CSS (plain, vanilla CSS) styling elements on your site.
Sass/SCSS (hereafter, Sass) does not replace CSS (you won't ever see <link type="text/sass">
), it simply provides a different syntax for writing styles that is later compiled into CSS.
Sass is typically compiled to CSS before you send your assets to production, it's not generated when a user requests it. There's no real connection between your Sass files and your HTML document so you would not be able to pass any variables to your Sass files.