Informal:
* "Hob a gut tsait" (האָב אַ גוט צײַט): This is the most common and straightforward way to say "have fun". It literally means "have a good time".
* "Geniesh dikh" (געניעס דיר): This means "enjoy yourself" and is a slightly more formal way to say "have fun".
More formal:
* "Fraylakh dikh" (פריילאַך דיר): This means "be joyful" and is a more poetic way to say "have fun".
In specific situations:
* "Hob a gut yom tov" (האָב אַ גוט יום טוב): This means "have a good holiday" and is used for specific holidays like Shabbat or Rosh Hashanah.
* "Hob a gut gefil" (האָב אַ גוט געפיל): This means "have a good feeling" and is used when wishing someone luck or success.
Ultimately, the best way to say "have fun" in Yiddish depends on your personal preference and the situation.