The Bangladesh team took a ferry for the 180km sea journey from Saint Lucia -- where they played the second Test -- to Dominica, but by the time they reached their destination on Thursday afternoon the effects of the sea had left them exhausted.
The touring side won the first two matches before India bounced back to level the series at 2-2.
India levelled the five-match series 2-2 after the visitors lost the fourth T20I by 82 runs.
Bhuvneshwar Kumar has been named vice-captain for the two-match series.
The two scored unbeaten fifties as South Africa chased down India's total of 211/4.
Skipper Harmanpreet Kaur (37) top-scored, while Harleen Deol (35) and Deandra Dottin (32) made useful contributions.
The Proteas have handed a maiden Twenty20 International call-up to batsman Tristan Stubbs, for the five-match tour of India starting on June 9.
The tournament, that usually alternates between ODI and T20I formats, was last played in 2018 and won by India.
Sanju slashed at a wide delivery from Kumara and Fernando pulled off a blinder at short third man.
The hosts have clinched the three-match T20I series 2-0.