Sanka, a decaffeinated coffee, is not only "SANs CAféine, or SANKA" it is freeze dried so it will disolve completely in boiling water.
A number of products are sold for the convenience of consumers who don't want to prepare their own coffee. Instant coffee has been dried into soluble powder or freeze dried into granules, which can be quickly dissolved in hot water for consumption.
Let's get simple. It's fair to say that while all Sanka is decaf, not all decaf is Sanka. Today, virtually every coffee company produces a decaf version.
Sanka is just a brand name. Since it was the first brand of decaf to become well-known in the U.S., people used the name for all types of decaf until recently. The orange-trimmed carafes used for Sanka now just signify "decaf" -- which may not be Sanka at all.
In Europe, when I want decaf, I order "Hag," (pronounced "Ahg," hard "g"), which was the original name of the decaf coffee that became Sanka in the U.S.