Directions from Pune - Get off at Kamshet station. Outside you can enquire for and get a jeep to Jambhivali (base) village. You could ask the local villagers for the route from here.There is also a route from Sandshi village.
Water is available at top in the cave, set in the cliff face. You can stay there overnite too. Caution - do not sleepwalk, else you'll fall right off!
The cave is also used for rituals like sacrificing chickens, etc to the god (Shankar or Bahiri in this case).
Ideally do not go on the 'religious' days as the villagers use the cave then.
Now, some unasked for advice and suggestions :)
If you are planning to take a group along - even if you know rock climbing, it would be advisable to go prepared with ropes, etc. and knowlege and training in how to use them. There is no margin for error on that patch. A fall can result into eternal oblivion.
Ascending the last top patch is not recommended towards evening. Best done early morning with lots of day time ahead and to avoid climbing in heat.
The villagers all climb to that cave barefoot, wearing polyster trousers and shirts! (Only the men among them go there due to religious restrictions.) They dont use any rope etc, but then I guess they are used to the mountains and the hills in a way we city bred people are not. I tried walking without my shoes at one point, but the stone was too hot.
I forgot to mention the best part tho'. The first part of this trek takes you for a considerable distance through a decently dense jungle. You come out towards the top at a narrow and steep gully. You have to climb down this, to take the path that takes you to the cave. As we sat at the entrance of this gully for a breather, I was surprised to see a horde of butterflies - crimson rose, blue mormons, limes, common crows, tigers, etc, emerging. Probably from the forest valley below. It was lovely!
There are also beehives somewhere around. You will see some photos of this trek in posts below.