Your Question is too vague, you need to be a little specific, India has innumerable offbeat destinations and one may take several years to cover them (if one takes 4 to 5 tours annually). First you need to be specific on theme of tour you are looking for I.e., Mountains, Beaches, Old Monuments / Heritage, Sand Dunes, temples etc. Whether you are a party lover or seeking peace and tranquility. Which City you are located and how many days tour you are looking for. You wish to go solo or with family or couple or in a group. You want to fly or go by road. I would suggest you to read suggestions in various Tripoto Articles available on their website and also being published from time to time by them for such destinations, you will get beautiful insight.
Halebidu Karnataka for architecture
Chembra peak wayanad popular for picturesque views
Majuli Assam famous for clean waters
Champaner Gujarath an offbeat historical spot that has existed from Ramayana era
Hemis Jammu and Kashmir where if u lucky you get to see snow leopard
Mandu Madhyapradesh an architecture masterpiece
Lunglei Mizoram a paradise on its own
Mokokchung Nagaland which gives u insight of Ao village lifestyle
Theog Shimla an awesome hilly region
are a few offbeat spots to explore.
https://tripoto.page.link/VNsnyC3M7BZAhdaZ7
Kindly check the above link for more info.