There's tons of things you can do, most are online due to the robust/flexible nature of the internet.
I've tried stuff from doing Airbnb arbitrage (you rent a place and sublet it on Airbnb for a higher price to make a spread).
I've done stuff with flipping art and collectibles on eBay.
I've done stuff like driving for Lyft.
I've done stuff like convincing folks online to pay for SEO services.
I've also played around with service arbitrage (you hire people for a lower price and sell the same service at a higher price).
Nowadays, I mostly do e-commerce.
Each has their pros & cons.
I've done a bunch of other stuff as well, but I've done way too much to remember. If you're interested, I document all kinds of other
misc tactics / side hustles ideas as well -- feel free to read 'em (I can only put one link per post but everything I've mentioned above, plus income reports are in the link--just search for "lyft" "ebay" etc to find the correct article). But I'd say the above list are probably the easiest / most lucrative.
Hope this helps.