Having lost to India by 105 runs in their lung opener, West Indies needed a victory to stay alive in the tournament.
The Caribbean islanders did it in style by rattling up their highest-ever ODI total of 368 for eight by riding on 21-year-old opener Stephanie Taylor's career-best knock of 171 and then bowled out Sri Lanka for 159 in 40 overs at the MIG Club ground.
Jamaican Taylor cracked her fourth one-day century and the hard-hitting Deandra Dottin smashed the fastest-ever half century in women's cricket in only 20 balls to power the West Indies to their first-ever 300-plus score and the fourth highest in the tournament's history and the seventh best of all ODI scores.
Sri Lanka, who had stunned defending champions England with a thrilling last-ball win in their tournament opener at the Brabourne Stadium two days ago, never threatened to surpass the target and lost comprehensively.
The West Indians bowled with purpose and also fielded brilliantly, in total contrast to the dismal show put up by their rivals, to emerge deserving winners.
Both teams are level on two points from two games in the four-team group which has opened up.
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Sri Lanka never recovered from their dismal start that saw them losing their openers Charmari Athapaththu and Yasoda Mendis with only 29 on the board.
They then slumped to 89 for six before finally collapsing for the modest score, with only Prasadini Weerakkody crossing 20 among top six batswomen by making 22.
Deepika Rasangika, at number seven, top-scored with 28 before being brilliantly caught by Shemaine Campbelle off Shaqana Quintayne. MORE