E way bill

one of my client has business of tea. He make supply of goods in his own vehicle (a van) . he supply goods when he go to his customers and he ask them for their demand and as per that he supply them goods.

so he want to ask that how E Way bill will be applicable on him. and as per the situations he cannot generate e way bill because he does not know the quantity of goods to be sold until he reach to his customers.

is there any way to fulfill the compliance requirement?