Spray
A spray is an object in the Pikmin games. It was found out in Pikmin 2 that one of the new plant species, dubbed the Burgeoning Spiderwort, can grow berries that have special compositions that can be used to your advantage, which is where sprays then come in. There are two kinds of sprays, both described here.
Ultra-spicy spray
See main article. (click above)
Obtained from the red berries. This spray is to be used on the Pikmin. When used, the Pikmin temporarily get enhanced strength and speed, and their leaves glow red. This is useful if they are losing a fight or need to hurry at the end of a day. The spray wears off in about a few minutes.
Ultra-bitter spray
See main article. (click above)
Obtained from the purple berries. This spray doesn't affect Pikmin (excluding 2-Player Mode), but is rather intended on enemies. When used, it will turn any enemies in the path of the spray into stone. It will last for several seconds (approximatyely 10 or more), but should be enough time anyway for the enemy to be killed, or weakened for that matter. There is a disadvantage, however, as the enemy will crumble when killed without a carcass to give you more Pikmin, but will leave behind nectar or sprays,.
Making Spray
Both types of sprays can be made by bringing 10 of the berry needed to Olimar's rocket, which will create a spray from the berries. Sprays can also be found in any places where nectar is, in the form of red or purple nectar drops. Each dose you find resting on the ground counts as one full spray. There are many other ways as well, but for that, you should consult the main articles.
Other
In demo images of Pikmin 2, there was a red spray, likely the Ultra-spicy spray, but also a yellow spray. No exact information is provided whether these were sprays at the time and if they truly did what the current sprays do now.