As you have asked about the best IIT coaching institute in Mumbai, I am giving you information about it, check below for the details

ALLEN Career Institute, Kandivali  
Coaching Center
Address: 4
th Floor, Thakur Cinema Mall, Above MC Donalds, Thakur Village, Kandivali (East), Mumbai, Maharashtra 400101
Phone:099875 32233

Rao IIT Academy - Top IIT JEE Coaching Classes Mumbai  
Coaching Center
Address:
302, Centre Square, Opp. Bharat Petrol Pump, Near Andheri Railway Station, Swami Vivekanand Road, Andheri West, Mumbai, Maharashtra 400058
Phone:091679 40593

IIT-ian's PACE  
Coaching Center
Address:
Office No. 201 to 208, 2nd Floor, Runwal Complex, Govandi Station Road, Opp ICICI Bank, Govandi East, Mumbai, Maharashtra 400088
Phone:022 6589 1583

Aakash Institute | Aakash IIT-JEE  
Educational Institution
Address: 6th Floor, Sunshine tower, Senapati Bapat Marg, Dadar(West), Mumbai, Mumbai-Dadar, Maharashtra 400013
Phone:022 3945 4545

Resonance IIT-Jee Coaching Institute  
Tutoring Service
Address: Mata Amritanandamayi Marg, Sector 22, Nerul, Navi Mumbai, Maharashtra 400706
Phone:1800 258 5555

IIT Point  
Networking Training Institute
Address: Flat No.101, 1st Floor, Ratan Apt., S.V. Road, Opposite Pantaloon Showroom, Borivali West, Mumbai, Maharashtra 400092
Phone:077188 28276