Database
[{CustomerId:123,CustomerName:"Some Company",Vehicles:[{Id:123456,Make:"Ford",Model:"Focus",FieldsToUpdate:false},{Id:543213,Make:"Kia",Model:"EV9",FieldsToUpdate:false}]},{CustomerId:123,CustomerName:"Some Company",Vehicles:[{Id:123456,Make:"Ford",Model:"Focus",FieldsToUpdate:false},{Id:543213,Make:"Kia",Model:"EV9",FieldsToUpdate:false},{Id:543219,Make:"Kia9",Model:"EV99",FieldsToUpdate:false}]}]
Query
db.collection.update({CustomerId:123,"Vehicles.Id":{$in:[123456,543219]}},{$set:{"Vehicles.$[x].FieldsToUpdate":true}},{"multi":true,"arrayFilters":[{"x.Id":{$in:[123456,543219]}}]})