Sourballs are a holiday exclusive topping available during Onionfest in Papa's Cupcakeria (All Star). The topping is unlocked on Rank 22 with Danny.
Sourballs is a standard shaker available in Papa's Freezeria DELUXE. The shaker is unlocked with Grace at Rank 56.
Sourballs is a standard shaker available in Papa's Freezeria Deluxe Refined. The shaker is unlocked on Day 33.
Sourballs is a standard shaker available in Papa's Cupcakeria Deluxe. The shaker is available from the start of the game.