Answer: By making them take selfies.
Uber announced on Wednesday updates to its policies during the coronavirus pandemic. Among the changes were limits to the number of passengers allowed in a car and updated requirements for masks.
Beginning Monday May 18, Uber will not allow rides for more than three passengers at a time. Riders will also not be allowed to sit in the passenger seat, in order to maintain social distancing between themselves and the driver. However, they will still be allowed to sit right next to each other in the back seat, since most riders these days are coming from the same household anyway.
Additionally, both riders and drivers will be required to wear masks. In order to make sure that they do so, drivers will be required to take selfies through the app, just like they already do for security purposes. The system will not allow them to take rides if it does not detect a mask in the image. Passengers do not have to verify that they are wearing a mask, however, drivers are encouraged to cancel a ride if the passenger(s) do not do so.