Synthetic filled bags can be hand washed in the same way as down bags to maximise their lifespan. However, they can also be carefully machine washed in a large front loader on a gentle cycle with a specialist sleeping bag soap or mild non-detergent soap.
Do not wash a sleeping bag in a top loader with an agitator as it will destroy your sleeping bag. Air drying is the best way to dry your sleeping bag. A synthetic filled bag will dry quicker than a down bag and is not quite as fragile when wet, but still take care to support the bag when wet.
Make sure you lie it flat to dry.