(See the Welcome & Intro and Vision & Rules Pages if you’re new here.)
The seemingly most obvious way for me to turn $1 into $2 was to go to the 99¢ store…

…buy some sort of snack there, then attempt to resell it to my coworkers. I see no reason why this strategy wouldn’t work for the first four or five powers of two.
My mom wanted to visit this store and I was hanging out with her, so I theoretically didn’t need to factor hours of my time into this effort. That said, I find grocery stores stressful so decided to “charge” for a half hour of my time anyway.
I perused the aisles and found this seemingly vegan box of frosted oatmeal cookies, for exactly $1 with no sales tax. Score.


So I guess to turn this $1 into $2, I sell the eight cookies for 25¢ a piece, which seems like a good deal on both ends.
Since Venmo seems to be the way that people pay each other in a cashless way, I opened a Venmo account and will allow people to pay me that way. It reduces the barrier and from what I can see, there are no fees for receiving money.
Like I said in the Vision and Rules page, I want to avoid advertising this effort to the people I’m selling to, but am breaking the rules for the initial powers of 2 (say up to $64) so that people don’t get weirded out by my charging for cookies at my workplace. So I’ll just print a small sign with this website and the cost and place it by the cookies. Hopefully it won’t cause too much of a distraction.
Outcome
I placed the cookies in a container with a sign. No one noticed them. In our group chat, when the first person said hello, I announced I had cookies for sale and a coworker who sat across from me was amused and bought all of the cookies for $2 within five minutes of making that announcement.