When in the nether if you quit while being affected by the withering affect all your stuff will disappear and you will remain in the nether gaining back all your health and hunger points

Step 1 enter the nether
Step 2 find a fortress
Step 3get hit by a wither skeleton
Step 4 quit the game when you have at most 3 hearts remaining
Step 5 join back on the world
After doing this all your stuff will disappear from your inventory and hit at including armor and offhand items