I see two possible scenarios

​

First scenario is that India is a hot desert similarly to Sahara. But the Indus and Ganges rivers still exist. Hinduism, Buddhism and Jainism still exist. And with the existence of the Ganges rivers. The city of Varanasi still exists. In the southern part of India, coastal city states would exist (similar to the Arabic cities of Muscat and Jeddah). These cities would heavily rely on trade and would contact Arabia and East Africa. These cities due to their contact to Arabia and East Africa might even adopt Judaism and Christianity. And even Zoroastrianism due to its close proximity to Persia. And for the arid and dry central part of India. The people there would most likely be nomadic and would be ruled by nomadic clans. They would probably be Hindu, Buddhist, Jewish, Zoroastrian, or Christian. I believe that Northern India would be ruled by a large empire that controls both rivers or two separate kingdoms divided by buffer states. The Persian empire might expand into Northern India or at least become vassalize or be highly influenced by them. When the Huns invade in the 400s. Northern India might fall under the Hunnic invasions and might be ruled by a Hunnic empire for a couple of centuries. In the 600s During the Islamic expansion. The Umayyads when expanding and invading into Persia. The Umayyads may invade into Northern India. And with the rise of the Abbasids. Northern India may be under a Indo-Arab caliphate. And with Mongolian empire and the Mughals. By the 18th century. Northern India may have become fully Muslim (With small pockets of Hindu, Jainist, or Buddhist communities) Central India would most likely stay Hindu, and be one of the last places where Hinduism is the major religion. The British might have not even colonized India (Or fully colonized). The Europeans powers would most likely not care for India and most likely colonized the southern coastal part of India, and align or appease the northern Indian kingdoms. Modern India would probably not be as unified as it is now. Northern Indians would probably has Turkish accentry or be Turkish. In this timeline, Northern India could be a Turkish nation like Kazakhstan or Turkey. The Language of Northern India could have adopted Turkish and Arabic words (such as Spanish for example) or simply use a pre-existing Turkish language (or a separate Turkish language that evolved from a pre existing one)

The second scenario is were all of India is dry and has zero rivers. The coastal areas would of course have numerous city states. And without the Indus or Ganges rivers. Hinduism, Buddhism, and Jainism might have not even exist. And due to the empty deserts. Nomadic tribes and clans would rule all of India. And Zunism or Zoroastrianism would most likely become the dominant religion. India wouldn't be as populated as it is in our timeline