Kusal Mendis hit career-best 86 off 55 balls to guide Sri Lanka to 174-7 in the third and final Twenty20 against Bangladesh on Saturday.
Bangladesh made regular breakthroughs after electing to bowl first in Sylhet and Kusal staged a lone show for the tourists, hitting six fours and as many sixes in his knock.
Taskin Ahmed struck early to remove Dhananjaya de Silva for eight before Rishad Hossain took the wicket of Kamindu Mendis for 12.
Kusal and returning captain Wanindu Hasaranga added 59 runs for the third wicket, with Hasaranga contributing just 15.
Mustafizur Rahman forced Hasaranga to give a catch at third man before Shoriful Islam dismissed Charith Asalanka for three.
Kusal raced past his previous best of 79 against New Zealand with a six off Shoriful after bringing his fifty off 35 balls.
Taskin ended his onslaught in his final spell during the 17th over as Soumya Sarkar took a high catch at midwicket.
Dasun Shanaka was the next top-scorer after Kusal. He hit 19 off nine balls before he was run out in the last delivery of the innings.
Bangladesh have never won a T20 series against Sri Lanka.
The series is currently locked at 1-1, with Sri Lanka winning the first match by three runs and Bangladesh triumphing by eight wickets two days later.
Bangladesh: Najmul Hossain Shanto (capt), Liton Das, Towhid Hridoy, Soumya Sarkar, Mahedi Hasan, Mahmudullah Riyad, Jaker Ali Anik, Rishad Hossain, Taskin Ahmed, Mustafizur Rahman, Shoriful Islam.
Sri Lanka: Wanindu Hasaranga (capt), Kusal Mendis, Kamindu Mendis, Sadeera Samarawickrama, Charith Asalanka, Angelo Mathews, Dasun Shanaka, Dhanajaya de Silva, Maheesh Theekshana, Nuwan Thushara, Binura Fernando.