Bulgaria's chances of reaching next year's finals vanished on Saturday when they lost 4-1 to Cyprus but Georgia scarcely had a shot on goal as the hosts tore into them from the start.
Manchester United's Berbatov completed his hat-trick within 29 minutes to take his Bulgaria tally to 46, just one goal short of Hristo Bonev's national record.
Martin Petrov scored twice and gritty midfielder Stanislav Angelov added another, his second international goal.
Bulgaria's triumph, seen by one of the smallest-ever crowds at the Vasil Levski national stadium, was helped by errors from Georgia keeper Giorgi Lomaia.
"You don't score six goals in a World Cup qualifier every day," said Bulgaria coach Stanimir Stoilov.
"The fans should believe in the national team and I hope we'll play in front of a capacity crowd next time."
Georgia finished the match with 10 men after Levan Khmaladze was sent off 13 minutes into the second half.
Berbatov said: "There's nothing unusual in Bulgaria's failure to reach the finals as we don't have quality players for every position.
"The fans should be realistic and accept the reality. There's a lot of work to be done."
