Joghurt is one of the few German words that can be used in all three genders (others are Dschungel and Wimpel). In Germany, it is most commonly masculine; rarely, it is neuter. In Switzerland and Austria, it is most commonly neuter; around Vienna, it is feminine.
When the word is masculine or neuter, its genitive is usually Joghurts. Very rarely, Joghurtes is found.
Some references, such as the Digitales Wörterbuch der deutschen Sprache, do not recognize the term as having a plural; nonetheless, one is attested (Joghurts).