Formal:
* Лека нощ и сладки сънища! (Leka nosht i sladki snishtya!) - This is the most common and polite way to say it.
Informal:
* Лека нощ! (Leka nosht!) - This means "goodnight" and is often used with friends and family.
* Приятни сънища! (Priyatni snishtya!) - This means "sweet dreams" and is a more casual way to say it.
* Сладки сънища! (Sladki snishtya!) - This also means "sweet dreams" and is another informal option.
You can also combine the formal and informal phrases:
* Лека нощ и приятни сънища! (Leka nosht i priyatni snishtya!) - This means "goodnight and sweet dreams" and is a good option for most situations.
No matter which phrase you choose, it's always polite to add a "добре си почивайте" (dobré si pochivaite) which means "rest well."