Setting Sass environment variables in Grunt
Here is a trick I used a few weeks back when I ran into the same issue as you are (were?) having. Although I've used grunt-contrib-sass I think the trick should translate quite well to grunt-sass. What I basically did was to define two environment files with the same name and placed them in different folders. Next I configured Compass through Grunt to use different include paths (pointing to the two different folders) based on the build target. My scss file setup was pretty much as follows :

sass/
  dev/
    _env.scss
  dist/
    _env.scss

  component/
    _stuff.scss

  main.scss


and my main.scss file opened with the line

@import "env";

// use env variables from here on


Next, in my case, I defined two compass tasks in my Gruntfile which, based on environment, would either add sass/dev or sass/dist to the include path, e.g. :

compass : {
  options : {
    sassDir : '&lt;%= project.app %&gt;/sass',
    // ... and other options
  },
  dev : {
    options : {
      importPath : ['&lt;%=project.app%&gt;/sass/dev']
    }
  },
  dist : {
    options : {
      importPath : ['&lt;%=project.app%&gt;/sass/dist']
    }
  }
}


Now by executing either compass:dist or compass:dev tasks the include paths differ which in turn result in the inclusion of the desired set of environment variables. For grunt-sass the same thing should be possible by setting the includePaths property (rather than importPath in grunt-contrib-sass). Hope that helps!