Summary

Attached is a ZIP file containing an advancement and a function. The advancement simply triggers for any inventory_changed, and rewards the player with the function.
The function updates the player's inventory. This behavior can be observed when the function clears the player's inventory or puts items there with /replaceitem. The function lastly revokes the advancement so it can be earned again.

Upon updating the inventory, the changes are not applied client-side. That is, if the player's inventory was cleared, it would still appear to contain ghost items. If the player was given items, they would not appear until the slot were updated somehow.