The Ultra-Spicy Spray is a very useful spray in Pikmin 2 and Pikmin 3 that will supercharge any Pikmin under your command for a short period of time. During this supercharged mode, they will perform all actions faster, be it fighting, running, carrying objects, tearing down walls or anything else. In order to get more Ultra Spicy Sprays, seek out red berries in the overworld. These are pretty easy to find, but the best place for them in Pikmin 2 is the Awakening Wood, as the plants that bear them grow right near your onions and rocket. Have the Pikmin carry the fruits back to the rocket, and you can make a spray with each ten berries you recover. Another good way to find these sprays is to flip over Iridescent Glint Beetles three times. They will give up two doses of the spray along with plenty of nectar and sometimes pellets. These creatures are rare, and the best places to look for them are the three caverns in the Wistful Wild as well as the Awakening Wood- two of them are hiding in special locations. In Pikmin 3 the best way to find those spray is to use the plant near the S.S. Drake in the Twilight River just across the river.
Best Use of the Spray
Undoubtedly the best use of this spray is against bosses, particularly some of the later ones- and especially the final boss. Enter dungeons with plenty of these sprays handy and you should emerge victorious after your clash on the final floor. In the game's challenge mode, these sprays also make collecting many treasures much easier in a shorter period of time.