Sindhu, the reigning world champion, defeated Denmark's Line Christophersen, ranked 24th in the world 21-19 21-9 on Thursday.
Sindhu looked sluggish in her first event in two months at last week's Denmark Open, where she lost in the quarterfinals to fast-rising Korean An Seyoung.
Loh Kean Yew defeated Lakshya Sen, who was the tournament's top seed and world no. 25, in 36 minutes to win his sixth international title.
The deadline for sending the entries had been extended twice, from September 10 to 15, and then to September 21.
It was India's second straight defeat after losing the Group A opener to Thailand, and the final match is against Finland on Wednesday.
India's mixed doubles pair of Pramod Bhagat and Palak Kohli lost 9-21, 21-15, 19-21 to Lucas Mazur and Faustine Noel of France.
In a three-game thriller, Ashwini Ponnappa and N Sikki Reddy lost to local favourites Freja Ravn and Amalie Magelund in the women’s doubles final.
The Hyderabadi shuttler's latest accomplishment is becoming the first Indian woman to win two Olympic individual medals.
PV Sindhu defeated China's He Bing Jiao in the bronze medal match, to become the first Indian woman to win two individual Olympic medals.
Day 9 of the Tokyo Olympics 2020 witnessed its fair share of excitement. Here are the highlights.