What Is The Stupidest, Simplest Business I Cannot Possibly Fuck Up?

I've been a cofounder of multiple tech startups, never had an exit. I have an MBA and have been a consultant. Ran a couple of 1-person small businesses in high school/college, just barely scraped by enough revenue to survive with a roof over my head. My current business is bootstrapped and is costing more than it's making.

I like #startuplife and am obsessed intellectually with business, but I might just fundamentally suck at making money. I need to know whether this is just statistics and the luck of the draw, or if I'm genuinely bad at this entrepreneurship thing and should stop trying for the rest of my life.

So I'd like to take a month or so and see: if I can't run the world's simplest possible business profitably, this is not for me and I should just go be an employee.

Awhile ago on this sub (I think) there was a wild thread about someone who rented out margarita machines at parties and made a killing with it. I'm looking for ideas like that. Or power washing? Coffee stand? Upcycling? Sell pet rocks at a farmer's market?

I have a few thousand dollars, some spare time, and a bizarre grab bag of skills from AI to editing to furniture refinishing and remodeling to scientific field work. I'm excellent at cleaning bathrooms. US west coast.

Nothing that has an "if you build it they will come" product risk, not another habit tracking app. Nothing with an annual commitment to ongoing maintenance. Nothing that requires signing a lease. I want to do a thing or make a thing and get paid for the thing. Simplest, dumbest thing possible. Other than that, all ears.