Ukrainian citizens who enter Romania by car and do not have the RCA policy and the Green Card can take out a border insurance, which is valid for 30 days in all states of the European Economic Area and in Switzerland. 

Vehicles considered uninsured are those for which the conclusion of MTPL insurance in Romania is mandatory and for which no valid insurance documents are presented (Green Card or Border Insurance issued in other states). More details can be found here.

The model of the document Border insurance can be found here here.

The list of countries not in the European Economic Area is available here.