This question is about a myth popular in India and Pakistan (as printed). The myth is that drinking water or milk after eating watermelon causes cholera.
Have any experiments falsified/supported this myth?
According to Wikipedia:
Cholera is an infection of the small intestine caused by the bacterium Vibrio cholerae.
Thus, if a watermelon or any water contains that bacterium, you will get cholera from consuming it. The combination does not matter. If you consume things that don't contain this bacterium, you will not get cholera, no matter which things or in which combination.