I tried several apps to make money from the phone, and honestly, there are more options than you might expect.

The easiest starting point is survey apps like Swagbucks and Survey Junkie – the earnings aren't huge, but you pass the time and earn a little.
If you have a specific skill, Upwork and Fiverr are the best for freelancing – there's high demand for writing, design, and programming.
If you have old stuff at home, eBay and Etsy help you get rid of it and make money.
Regarding investing, Robinhood and Acorns are options available, but you need to be cautious.
Cashback from Rakuten and Ibotta helps you at least get part of your money back when shopping.
Driving and delivery with Uber and DoorDash is an option if you have a car or free time.
The truth is, making money from apps on your phone varies depending on your situation and skills, so what works for one person might not work for another.
The important thing is to choose what suits you and read reviews before you start.
Honestly, some of these apps are much better than others, but all require patience and a little effort.