The Lucky Sandwich is an item in EarthBound. They can be first bought by Ness in a Drugstore in Onett. This item is relatively expensive, as it comes to a price of $128. Its primary function is a recover-type item.
Since this is a luck sandwich, it does numerous (and random) things to its user. It can either heal the player from a minimum to a maximum amount of HP, and a times, recovers a party member's PP to a minimum to the maximum. This item is based on the party member's luck, and the higher it is, the successful effect will go to that person.