Colombo: Dimuth Karunaratne won the toss and elected to bat first in the third ODI on Wednesday.
After losing opener Fernando so early (13/1), skipper Karunaratne and Kusal Parera took hold of the situation and made 83-run partnership for the second wicket.
The same was followed by Kusal Medis and Angelo Mathews as both of they build a solid partnership of 101 runs.
This took Sri Lanka towards a decent total.
Kusal Medis got out for 54 off 58 balls. Angelo Mathews made 87 off 90 balls before he departed in the 50th over.
A quick 14-ball 30 from Danus Shanaka also helped the team to reach close to 300.
Bangladesh faltered in their run chase yet again, with Soumya Sarkar (69) the only batsman to put up any sort of resistance.
Taijul Islam (39) came up with a brave effort at the end, but it was too little too late as Sri Lanka won by 122 runs to claim a 3-0 series whitewash.