I'm going crazy finding this fic, so I turn to you.
This was written pre-canon Cheerio!Blaine. Blaine joins the cheerios, but sue actually wants Kurt to come back. So he is especially cruel to Blaine (hoses him down with water in the cold, waxes him etc.) to pressure Kurt. Blaine takes it all in stride, and even gets the cheerleaders to be more harmonious and at the end Sue accepts him, and Kurt joins on the condition that they get a hotel room for themselves at the national competition.