No, drinking lemon and warm water does not prevent Covid19
According to Harvard T.H Chan India Research Center, “there is no evidence from the current outbreak that eating garlic or lemon (or other foods for that matter) has protected people from coronavirus.”
A news article from Global News also states that although drinking water is healthy, it does not protect one from being infected by coronavirus.
The World Health Organisation (WHO) also states that drinking water can not prevent one from Covid19 infection. WHO urges individuals to visit a health care provider if they have flu-like symptoms with a history of travel.
Source : multiple sources online have claimed that drinking water with lemon can help prevent the spread of Covid19.
Background : According to WHO, there is a total of 693 224 confirmed cases of Covid19 globally and 33 106 deaths.
Zimbabwe has recorded 8 confirmed cases and 1 death.