Drinking hot water with lemon helps to stay hydrated, but will not prevent or cure COVID-19 infection.
Drinking or gargling warm water with turmeric and salt can help with a sore throat, cold, and flu, but it will not protect against COVID-19 infection. The World Health Organisation(WHO) states that there is no scientific evidence that lemon with hot water helps prevent COVID-19. It further recommends that we much consume more fruits and vegetables to maintain a healthy diet to boost our immune system. A vaccine for COVID-19 has not been discovered yet, and currently, several potential vaccines are at different stages of clinical trials across the world.
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.