What is hi in Bulgaria?

"Здрасти" [zdrA-sti], which is considered impolite to say to someone you don't know.

Alternatively, you can use the more polite way, which equals "Hello" in English :

"Здравей" [zdra-vEi] - singular, unofficial way, usually to someone you know personally

or

"Здравейте" [zdra-vEi-te] - singular, official way to someone you don't know personally, or want to show respect towards; the same form is used for plural - if you're saying "Hello" to more than one person at once.