Unless this is somehow tied to the Lyft Company (i.e. Based on a True Story with names changed to protect the innocent/guilty) I would make your company a homage/parody of Lyft. This also gets you some creative license to add Uber features. I recommend the company name of Ryde, which gives you the distinct spelling style so its obvious who you're talking about. I would change the title to be either "Sex Confessions of a Ryde Driver", "Sex Confessions of a Ryde-Share Driver", or "Sex Confessions of a Ride-Share Driver". In the last, the industry being satirized is obvious and you don't rely on people knowing your fictional company. The former preserves your title but relies on understanding the misspelled company name (you could stylize it a bit better) and the middle gives you a mix of both worlds (Ryde-Share could even be worked into the book in universe as the original name of the company before it rebranded itself as just "Ryde", sort of like Facebook used to be "The Facebook". Your character could have been with the company so long that he was there for the original name OR he is such a nerd for the company that he would know this bit of Trivia lost on the general public).
The real secret of how to avoid getting sued for defimation is how much money you make off this book... if you don't make any, Lyft isn't going to pay lawyers to shut you up... that will only make more people buy the book to see what all the fuss is about.