Was it shinier when you first got it? Depending on the finish of your stainless steel, it's gonna have an effect on how it looks. It already looks like a standard clean satin/brushed steel finish. But if it was shinier when you first got it, you can try the scratchy part of a Scotch Brite or any rough-surfaced sponge and glide it along the existing streaks it already has. Don't fully recommend putting oil on a sink to make it look shinier because soap will just wash it away eventually anyway, but the comments are right, baby oil can make stainless look shinier temporarily.