The consumption of bitter gourd or its juice cannot prevent or cure the coronavirus disease, and there is no cure for it as of yet.
The Press Information Bureau debunked the claim in a tweet that drinking bitter gourd juice or consuming it in any form cannot cure COVID-19. As of now, the World Health Organisation or any other official authority in the world has not stated that a cure is available for the disease or that it can be prevented by consumption of any juice.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.