EDIT: And again I didn't search hard enough. I was searching for "interior" before, after I changed that to "room" I quickly found SET_ROOM_FOR_CAR_BY_KEY.
Here's C++ function:
| static void SetRoomForCarByKey(Vehicle vehicle, eInteriorRoomKey key)|
NativeInvoke::Invoke<NATIVE_SET_ROOM_FOR_CAR_BY_KEY, ScriptVoid>(vehicle, key);
You can find key using GetKeyForCharInRoom for example.