Max Syrup Jars are used in battle to refill a Bro's BP completely.
Max Syrup Jars will restore 40 Special Points. In the remake, Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, they refill a Bro's BP entirely.
These items will heal 80 BP for either Bro in this game. They retain their abilities in Mario & Luigi: Paper Jam. They can be purchased from item shops later in the game.