With Contraptions DLC, you can manufacture Vault tec lunch boxes. these are different than the ones you find in the wild as when you activate these ones they pop into your inventory rather than popping open and giving you random loot.

However you can still open them like their wild wasteland counterparts, by simply punching them(easy to do with knuckles equipped.) they will pop open and drop a random item.

The trick is that when these busted lunch boxes enter into either a hopper or a conveyor storage they are converted back into their intact state.

as can be seen by the screenshot below, a simple loop can be built that will allow you to endlessly punch open the Lunch boxes, sort out the loot and put the broken boxes back into the hopper to start the cycle all over again.
Complete Loop


The (Item) Sorter is set to filter out all the loot except the lunch boxes, which will pass straight thru, while the loot will be diverted into a conveyor storage.

The hopper can be controlled by either a switch or a pressure plate. This is a good idea to implement.
prevent the boxes from just looping endlessly when your not around, which can be a problem with how glitchy the physics can be at times.

Vault tec lunch boxes can be built using the builder, they only require 3 steel to make per box. building about 25 to 30 pretty much ensures an endless stream of boxes to punch open.

Doing this it's possible to farm cork (from baseballs, also useful for making baseball grenades), nuka cola, noodle cups, fusion cores and the robot models. you'll also gain more steel do to table knives, forks and spoons being possible loot, allowing you to farm steel for making bottle cap mines (IE, Making more lunch boxes).


Special Note: It has been brought to my attention that in order for this to work for everybody, you should ensure you have one intact lunch box in the hopper before the broken ones drop in. personally i had zero issues with this, but some have reported this as a potential issue. so if my guide isn't working, then try keeping a few intact boxes in the hopper at all times. if you have between 20 and 30 boxes you should be able to run this setup non stop with zero issues other than base balls getting stuck on the belts(due to rolling the wrong way).

A special thanks to Skooled Zone on youtube for discovering this trick.
Show him some love:
While he shows a basic way to do it, his method is clunky as it requires you to manually collect items and drag move the broken boxes. Still, his video inspired this guide.

Skooled Zone's Youtube Channel