Lisa, I use a commercial laundry for my business.
They lay them out brush them with a soapy solution and then power wash then off on a lowish pressure before putting them in a huge cold was machine with a regular branded soap powder.
Mild/diluted truck wash is used on plastic surfaces to get dirt grease and stains off and they just brush with a soft broom and then it goes in the same cold wash.
I just use a soapy solution and lay it on a sheet in our driveway, I give it a quick careful spray off and then I wash it out panel by panel in the bath and leave it too dry hung in the garage.
Soap will not hurt most Awning fabrics and avoid heat and strong chemical cleaning solutions.
A good cool long soak does no harm to loosen dirt.
If you need to proof the Awning do not waste money on spray cans, buy a big can of fabsil gold from a good camping shop and slop it on soaking it in gloved hands with a sponge.
Make sure you do it some time before you use it so the smell goes away.