First time in Sion Mumbai (http://triphippies.com/sion-mumbai/), and confused about what to eat? Start with Gurukripa, their South Indian breakfast is legendary among locals. The vada pav stalls outside the station are honestly some of the best I've had in all of Mumbai. Don't skip the pav bhaji in the evening, loaded with extra butter, obviously!
The whole area has this old-school Mumbai food culture that feels very authentic and unhurried. Absolute foodie paradise!