Microfibre couches can't be cleaned with soap and water because that leaves ugly stains. If your furniture is looking grimy, try rubbing alcohol instead.
With a bit of rubbing alcohol (aka isopropyl alcohol) and a white sponge, you can get some pretty surprising results on microfibre furniture. Just be sure to use a wide spray on the couch.
Sometimes, cleaning with rubbing alcohol can leave the fabric feeling a bit stiff. In that case, you can fluff the fibres with a soft scrub brush.
How to Clean a Microfiber Couch (or Sofa) [One Good Thing]