A few weeks ago Uber introduced Local Offers in cooperation with Visa.
The way it works is that you activate an offer from nearby stores (and chains) and then pay with the same Visa card that is on file with Uber. PayPal used to run a similar offer that would give you $5 a participating store when paying with PayPal.
Most offers are 2x or 4x points per dollar on your FIRST purchase only. They are also capped at 200 points. However 200 points equal $20 in free Uber rides!
In San Francisco many stores that participate sell store gift cards or (in the case of Walgreens) also sell Visa and PayPal gift cards. Since many offers are 4x, all you need to do is spend $50 in your first transaction to get the full 200 points. A $50 Visa gift card comes with a $4.95 price tag but you’d get $20 in free Uber rides.
The offers seem to be not targeted (though you can only add a certain number to your account at any time) and are available for EVERY Uber account. All you need is a Visa card (that might be a prepaid card to begin with).
This $20 is a free ride to the airport in many places (in SF it is enough for an Uber Pool to the airport).