Thank you!
Do you know if applying for OCI is an option while in India on an evisa?
No. Only on Entry Visa you can and after living in India continuously for 6 months
https://ociservices.gov.in/
A foreign national, - (i) who was a citizen of India at the time of, or at any time after 26th January, 1950; or (ii) who was eligible to become a citizen of India on 26th January, 1950; or (iii) who belonged to a territory that became part of India after 15th August, 1947; or (iv) who is a child or a grandchild or a great grandchild of such a citizen; or (v) who is a minor child of such persons mentioned above; or (vi) who is a minor child and whose both parents are citizens of India or one of the parents is a citizen of India - is eligible for registration as OCI cardholder. Besides, spouse of foreign origin of a citizen of India or spouse of foreign origin of an Overseas Citizen of India Cardholder and whose marriage has been registered and subsisted for a continuous period of not less than two years immediately preceding the presentation of the application is also eligible for registration as OCI cardholder. However, no person, who or either of whose parents or grandparents or great grandparents is or had been a citizen of Pakistan, Bangladesh or such other country as the Central Government may, by notification in the Official Gazette, specify, shall be eligible for registration as an Overseas Citizen of India Cardholder.
Foreign nationals cannot apply for OCI in India while on Tourist Visa, Missionary Visa and Mountaineering Visa. Moreover, the foreigner has to be ordinarily resident of India to be eligible to apply for OCI registration in India.
Note: 'ordinarily resident' will mean a person staying in a particular country or in India for a continuous period of 6 months.