Ultra-Sweet Spray is found in the Bramble Woods in Pikmin SP. It is found along with all the other spray berries, in a hollow near the landing site, guarded by a Black Bramble Gate. This spray is for use on Pikmin. When sprayed, the Pikmin will take 5 seconds longer to eat.
In Pikmin: The Final Frontier, this spray is yellow and is used on enemies. This slows them down for about 15-20 seconds. It is first found in The Aqua Garden.