This dupe it is an ancient dupe but it still works and it works on any DayZ mod (Origins, Epoch well you get the point)
This requires you to have a backpack with items that you want duped a vehicle or something you can drop it into and access to your ethernet cable or a way to turn of your internet.
Step 1: Have items you want duped inside your backpack
Step 2: Go into the gear menu in the vehicle or storage you can drop your backpack into.
Step 3: Highlight your backpack in preparation to drop it inside whatever you have to drop it into.
Step 4: Pull your ethernet cable or turn off your internet and drop your backpack into the gear of whatever you have.
Step 6: Exit to the lobby and reinsert your ethernet cable or turn your internet on.
Step 7: Re-enter the server
Upon entering the server you will have the backpack on your back and where you dropped the bag into you will find an exact copy of your backpack and items.
If this doesn't work try it again as sometimes it can be buggy and yes it does work on Epoch even with the countdown timer but it will show people that you are losing connection.
This still works as i still use it.
Enjoy and have fun.