How do I get rid of strong dog odor on my fabric sofa, I have tried many products but it is still there I have even washed it down with diluted vinegar but no joy.

Have you tried using baking soda? It has an odor eliminating effect. Just sprinkle it directly on the sofa and let it sit for a while. Than vacuum the sofa.

One product my sister and I tried was pet fresh. It worked on the carpet and I'm sure you could try it on the sofa too.

Also try keeping the dogs or other pets out of the room while you try these so that they don't try to lick the sofa.

Are you trying to eliminate general doggy smells or urine smells?

Doggy smells, I have had good luck with Febreze-type products. To a limited extent they have also helped with where my cat has marked.

If it is urine, then an enzyme based cleaner might work better for you.

Is it a 'doggy' smell or is it now a 'musty' smell?

For carpets I use baking soda, but it would quite possible work on furniture as well.
I just sprinkle baking soda on the area, leave it a while and then vaccuum it up. The baking soda neutralizes the smell and soaks up any moisture.

Febreeze as cat mentioned is fantastic, you don't want products that cover up the smell as it will just eventually come back, you need an enzyme based cleaner to actually remove the smell.

Yes to eliminate doggy smell, you need to get to the source. If your dog has a strong odour, he may need some additional faty oils in his diet. If you're not washing already, I would (if the funds are avalibe) go to the vet, ask about allgery shampoo's. The one I use is called Allergroom, it is made by Virbac, it's $15 dollars Canadian. The Omgea oils I use are called Aller G-3 capsules, and they were about 12$ can. For a bottel of 160. They have worked wonders for my smelly girl. A smelly dog can indicate food allergies among other things, like a mouth or gum infection.
If it's soiled due to urine or poo, then the above mentioned is usually a no fail. You can try a specific pet stain and odour remover found at walmart, just make sure you follow directions for use.

There is a brand called Spot Shot or something and it eliminates oder of pets. You can find it at pet Smart and all those pet stores.