If you truly believe that your vial and compound within that vial are sterile...were produced in a sterile environment, then sterile water and saline are fine.
If as is more likely your vial and compound within that vial was not produced in a sterile environment, then you need some Benzyl Alcohol to prevent the multiplication of bacteria. In addition although it is far from the best sterilizing agent, it does have some effect on killing some bacteria. Long ago it was used to sterilize cow teets.
Bacteriostatic Water contains Benzyl Alcohol and is a "safer" reconstituant then sterile water & saline.