Let us be honest, Indians are dirty with their obsession of defecating outside their house and drinking cow urine and pasting themselves in cow faeces.
BD and Pakistan may still be dirty but at least they do not do the above and so are a little cleaner.
One basic way to look at how clean a country is to look at the percentage of slum population in urban areas and the decline over time.
Population living in slums (% of urban population) - Bangladesh from The World Bank: Data
data.worldbank.org
BD has gone down from 87.3% in 1990 to 47% in 2018
India has gone down from 55% in 1990 to 35% in 2018
Pakistan has gone down from 51% in 1990 to 40% in 2018
So BD seems to be making the most progress but of course it was easier as it came from a much larger share of urban slum population. All 3 countries should make a determined effort to bring the slum population below 10% within the next 10-20 years.
In addition they need to make sure that household and industrial waste is properly disposed of and the population learn and practice clean habits outside their homes.
It can be done but the strong guidance needs to come from the governments.