Only last week Luhut Pandjaitan, Indonesia’s maritime minister and close confidant of the country’s president, touted herbal mangosteen juice as a coronavirus remedy.

His suggestion was the latest in a string of unorthodox treatments put forward by the president’s cabinet over the past six months, ranging from prayer to rice wrapped in banana-leaf to eucalyptus necklaces.

The remedies reflect the unscientific approach to battling the coronavirus in the world’s fourth-most populous country, where the rate of testing...