As a general rule, artificial grass shampoo is the best cleaner. It removes dust, pollen and pollutants carried by the air. If you want to your grass, use clean water spread evenly and dampened without saturating it with water; never use water from a polluted source.
Aqueous : Remove any solid waste with a spatula. Clean any remaining marks with soapy water.
Non-aqueous : Non-aqueous (Beer, blood, chocolate, coffee, cola drinks, fruit drinks, sodas, glue, ice cream, milk, mustard, tomato sauce, tea, urine etc.) : Brush the residue using a stiff bristle brush. Rub using soapy tepid water or a non-abrasive household detergent. Rinse copiously in clear water. Wipe the grass using dry and clean absorbent paper towels.
Non-aqueous : Use a 3% dilution of ammonia.
Mop up with a mixture of alcohol vinegar and water, mixed in equal parts. Rinse copiously in water after application.
Spray with a freon aerosol or apply dry ice.
Scrape off with a cloth to remove the residue.
Use a biocide. Caution: beware of pressurised water sprays which could damage your grass.