I have setup a new project to test Foundation 6 using Gulp and Sass but it doesn't seem to compile at all. There is another post close to this topic, but I personally believe the accepted answer is not the correct solution - as it includes all of the components and is actually the opposite of what Zurb suggests (see this issue: https://github.com/zurb/foundation-sites/issues/7537). Anyway...
I installed Foundation 6.1.1 from bower, and added the path to my gulp-sass function in gulpfile.js like so:
// Compile Our Sass
gulp.task('sass', function() {
    return gulp.src('scss/theme.scss')
        .pipe(sass({ includePaths : ['bower_components/foundation-sites/scss'], outputStyle: 'expanded'}).on('error', sass.logError))
        .pipe(gulp.dest('css/'))
});
My theme.scss is as follows:
//vendor file
@import '../bower_components/foundation-sites/scss/settings/settings';
@import '../bower_components/foundation-sites/scss/foundation';
body{
  background: red;
}
When compiling my scss I get no errors, but the output of theme.css looks like this:
/**
 * Foundation for Sites by ZURB
 * Version 6.1.1
 * foundation.zurb.com
 * Licensed under MIT Open Source
 */
body {
  background: red;
}
So it appears it is hitting the file since the comment is outputted but its not compiling any of the Sass imports in foundation.scss.