Going from Bulgarian to Telugu (తెలుగు) has a composite linguistic distance of 90% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Cyrillic → Telugu
Indo-European ↔ Dravidian
The 5 languages with the lowest linguistic distance from Bulgarian:
A quick 3-question check between Bulgarian and Telugu. No signup.