According to the WHO, tap water is safe for consumption for 98% of the country.
Bulgarian tap water is generally safe and drinkable but may have an odd taste. Bottled mineral water is widely available and cheap.
According to the CDC tap water is generally not safe for consumption.
According to the Numbeo water drinkability and accessibility index, tap water has a score of 69.53 / 100 (100 being best).
Numbeo considers this score to be "High"
Bulgaria is a member of the European Union which ensures tap water safety across its countries.
1 adult could save about 402$ per year in Bulgaria by drinking tap water instead of buying bottled water.
๐ณ Drinking tap water would also help with reducing your plastic footprint and improve environmental pollution.
Like in most countries, water quality and accessibility differs from location to location, therefore it's the best to check the information available on that place.