<===> input.scss
@function map-each($map) {
  $values: ();

  @each $key, $value in $map {
    $values: append($values, $value);
  }

  @return $values;
}

$map: (foo: bar);

.test {
  -map-test: map-each($map);
}

<===> output.css
.test {
  -map-test: bar;
}