Micro Batteries with BMS! 3.6v 0.68wh - Shelf H1
Stop the cuteness!!!
Micro batteries for just 30 cents each. They have a BMS too, There are 2 pins on the top of the battery that you would connect to or simply cut open the plastic enclosure to gain access to the cell.
These came out of tiny medical batteries.
If you have any micro-projects in mind or want to build the world's smallest powerwall these would be a great option.