Sciencewater

 was a limited-time currency released on June 14, 2016 as part of the Superheroes 2016 Event. It was used to heal up to two hearts worth of life to the player's fighters, but only during a battle, be it in the player's town or in the neighbours' town.

How to Obtain
It can be obtained,
 * As a drop from Criminals, with a 3% chance of happening.
 * Completing event themed Daily Challenges.
 * Purchased for 2 Donuts each, but only if the player to heal their fighters without any  remaining.

Packages
Packs containing different amounts could be obtained as prizes:

US$