Instant Jusenkyo

Instant Jusenkyo, also referred to as Instant Jusenkyo Spring or Instant Jusenkyo Powder, is an fan-made name for a magical item seen in the Dojo Destroyer Arc and its anime adaptation, Danger at the Tendo Dojo!

Taking the form of a crystalline powder, Instant Jusenkyo is a magical dust purchased by Shampoo from Jusenkyo itself through unknown methods. There are implicitly many different varieties of Instant Jusenkyo, corresponding to the various springs, with the only one seen in canon being the Instant Nanniichuan Powder. Exactly how Instant Jusenkyo is made is unknown.

Powers
When applied to water, Instant Jusenkyo transforms that water into a "one-use" sample of Jusenkyo water taken from the appropriate spring - for example, Instant Nanniichuan Powder would transform the water it is applied to into a dose of Instant Nanniichuan.

Instant Jusenkyo Water functions almost identically to normal Jusenkyo water, but with the caveat that the transformation is a one-time-only change. If used on a being who does not have a Jusenkyo curse, once that creature has been splashed with hot water, subsequent doses of cold water will not transform them again. If used on a being who does have a Jusenkyo curse, then the next application of cold water will trigger their normal Jusenkyo curse.

It is unknown how long Instant Jusenkyo Water retains its powers if allowed to sit in a container.

Trivia

 * In the manga, it is implied that Shampoo was unaware of the one-time nature of Instant Jusenkyo until Cologne told her.
 * In both the manga and the anime, Ranma Saotome and Genma Saotome are shown to be able to use Instant Nanniichuan to temporarily cure themselves of their standard Jusenkyo curses... until they are exposed to a new source of cold water in the form of a sudden evening shower.
 * It is possible that Shampoo bought the Instant Nanniichuan through the same "Jusenkyo Products" mail-order catalog from which she would later order Waterproof Soap.

Dried Jusenkyo
A variant of Instant Jusenkyo appears in the anime-exclusive story Back to the Way We Were... Please! This version is more potent than the Instant Jusenkyo variant, and the artificial Jusenkyo water it creates functions identically to the actual cursed spring water. This means that a curse given through Dried Jusenkyo Water is permanent, unlike the Instant Jusenkyo giving one-time only curses. This is made explicit at the episode's start, when Ranma brings up his previous experience with Instant Jusenkyo water, and the nameless salesman assures him of the difference.

Three packets of Dried Jusenkyo appear in the episode, though their labels have been lost thanks to inadvertent water damage. Ranma Saotome, Ryoga Hibiki and Mousse all hope to benefit from a packet of Dried Nanniichuan, which unfortunately they end up spilling before they can use it. Dried Jusenkyo Water from the Springs of Drowned Pterodactyl and Sabertooth Tiger are seen in action, cursing once-normal animals.

As with Instant Jusenkyo, it is unknown how Dried Jusenkyo is made, and likewise what causes the difference between the two products.