Use code: OMRIDE100.

Terms and conditions

Maximum cashback amount is 100% of the ride amount or Rs. 100 which ever is lesser
Offer valid only on application of the coupon code OMRIDE100 before each ride
Offer valid on 1 ride
Offer valid for 7 days after the communication is received
Offer valid for selected users who get the communication
Rs.100 minimum Ola Money balance required before each ride
Ola Money and Ola Cabs reserves the right to withdraw/ modify the offer at its discretion

https://blog.olacabs.com/25-cashback-on-5-rides/