Items need to dupe:
Injection Vial
Syringe from Medikit

1: Put medikit on ground
2: drag syringe from medikit to injection vial in backpack
3: Choose to fill up syringe
4: Original syringe back in medikit and a new syringe(pristine) appears in inventory

When I had my medikit on the ground, I dragged the syringe to the injection vial and chose to fill it. When I did, the original syringe(damage 50%) automatically went back to the medikit, while a new syringe appeared in my inventory (100% condition).

I did this 3 times and dropped the new syringes on the floor and they all appeared normally. However all the new syringes (pristine) are filled with clear liquid.