Syrups are items encountered in many Mario RPG series games and they heal SP for Mario, Luigi, or Bowser so that they can use Special Attacks more often. They appear in all of the Mario RPG series, except for Mario & Luigi: Partners in Time.
Super Mario RPG: Legend of the Seven Stars
Syrups first appear in Super Mario RPG: Legend of the Seven Stars and this game doesn't contain regular Syrups. Instead, they were called Honey Syrups that would heal 10 FP to Mario and the Maple Syrup heals 40 FP, while the Royal Syrup heals all of the FP of Mario.
Paper Mario series
Syrups appear in all three Paper Mario series games as items used to heal FP again.
In Paper Mario, syrups come with a Mushroom that is bought from Mario, except the Life Shrooms, Volt Shrooms, and an Ultra Shroom. The regular Mushroom comes with the Honey Syrup item and the Super Shroom comes with the Honey Syrup. The Honey Syrup restores 5 FP to Mario while the Honey Syrup does 10 FP to him.Syrups reappear in Paper Mario: The Thousand-Year Door with all of the syrups from its predecessor reappearing and having the same effect. In this game, two new types of Syrups appear with them being the Gradual Syrup which slowly restores HP each turn and the Nitro Honey Syrup is a new type of Syrup that also appears.
Syrups make another appearance in Super Paper Mario with all of the Syrups reappear from the two previous Paper Mario series games, except for the Nitro Honey Syrup. Two new syrups, the Sap Syrup and the Dayzee Syrup appear in this game and restore HP to the player.
Mario & Luigi series
Syrups appear in Mario & Luigi: Superstar Saga and Mario & Luigi: Bowser's Inside Story as items that restore Mario and Luigi's BP (Mario & Luigi: Superstar Saga) or SP (Mario & Luigi: Bowser's Inside Story).
Syrups appear in Mario & Luigi: Superstar Saga as items that restore Mario or Luigi's BP with it restoring 20 BP total. There are three new types of syrups in this game known as Super Syrup which restores 40 BP total, the Ultra Syrup which restores 100 BP total and the Max Syrup which restores all of the BP of a Bro.
Syrups make their latest appearance in Mario & Luigi: Bowser's Inside Story as items that would heal Mario and Luigi's SP instead, due to SP replacing BP from Mario & Luigi: Superstar Saga. There are four different types of Syrups. Syrups (often known as Syrup Jars in this game) would restore 10 SP, Supersyrup Jars would restore 20 SP, Ultrasyrup Jars would restore 30 SP, and the Max Syrups would restore 40 SP instead of all SP like Mario & Luigi: Superstar Saga did.