To someone who speak Creole, say "Bon Saba"

To someone who speak French, say "Bon Sabbat"

To someone who speak English, say "Happy Sabbath"

To someone who speaks Norwegian, say "God Sabbat"

To someone who speak Spanish, say "Feliz Sabado"

To someone who speaks Italian, say "Felice Sabato"

To someone who speak Tagalog, say "Magandang Sabado"

To someone who speak Korean, say "Ansigil jal boneseyo"

To someone who speak Russian, say "Schastlivye Subbotu"

To someone who speaks Chinese, say "ān xī rì kuài lè"

To someone who speaks Bulgarian, say "Shtastliv Subota"

To someone who speaks Hindi, say "khuśa sabta"

To someone who speaks Greek, say "ef̱tychisméno sávvato"

To someone who speaks German, say "Glücklich Sabbat"

To someone who speaks Japanese, say "YO-ee ahn-so-ku-nee-chee-o"

To someone who speaks Cherokee, say "oo-lee-hay-lee-sdee gah-luh-kwoo-dee-yoo ee-gah O_O"

To someone who speaks Samoan, say "Manuia le Sapati"

To someone who speaks Hawaiian, say "Hau'oli La Sabati"

To someone who speaks Chinese, say "ahn-shee-rih kwy-lu" 

To someone who speaks Swahili, say "Sabato njema"

To someone who speaks Thai, say "suk-san-wan-sa-ba-to"

To someone who speaks Arabic, say "sah-BAHT sah-EED"

Remark: In French and in Creole, we pronounce Happy Sabbath exactly the same way.

Source: This idea is from Leo [::God's Warrior::] on October 16, 2011 on AYS.