Petrol stations in Taipei (Taiwan) had always given a free mask (nonwoven surgical type) to two wheeler drivers when they buy petrol+oil above a certain price in NT$. Quite often many of these gas-station masks are tossed into the storage compartment under the seat. When they offer a ride to someone else, the drivers often offer a new mask to the pillion rider from their stockpile. This mask will surely stop them from spreading their sneezes or coughs to others. In India I have seen girls wrapping their duppattah around their nose and mouth when they are driving a two wheeler. The masks protect them from particles from exhaust as well as other sources. The multi-layer cotton masks with pockets to insert a filter (sponge or nonwoven) are quite good. It would take about an hour or so to make one by hand, if one does not own a sewing machine. For insert filters, no need to buy anything -- people can just fold multiple layers of cloth, and use that.