I need ride but just have cash
The Guru Take
Generally not, but Uber started accepting cash in limited cities
For taxis, yes, almost all companies/drivers in all location would accept cash.
If you are referring to Uber and Lyft, they currently do not allow you to pay in cash, as the mobile app requires you to have your credit card or debit card in the system.
There are certain Uber services and in certain regions, cash can be used in lieu of the credit card on file. They are usually local taxis that you dispatch through Uber app (i.e. UberTaxi), but recently, Uber is starting to acecpt cash in more and more US cities.
Check out the "payment options" and if you see "CASH", that means they will allow it. You simply hand the cash over to the driver at the end of the trip. (https://help.uber.com/h/cae4b926-03d6-4ebf-81c4-75953ef54c0c)
What Uber services can I pay using cash?
Can i get a ride with cash only?

Comments
A friend needed to send money urgently but was unsure about a verification step. She looked up how to contact cash app to know what support options were available. Seeing how other users handled similar situations gave her confidence. She completed her transfer successfully, and having that information beforehand prevented unnecessary stress.
A complete stranger approached my car and asked if I would give them a ride "somewhere" for sixty bucks. I declined. I just thought that with so many Uber and Lyft drivers around, the person would have called one of them. But maybe the Uber or Lyft drivers here do not take cash. Either way, I can do without the visions of being told to drive down a dark road at gunpoint.