I once did that with a Samsung powerbank I have. Daisy chained the powerbank to charge itself and a phone in sequence.
The only thing that failed afterwards was one of the cables, but suffering a loss was definitely the reason I didn’t attempt to do that again.
Very true, those can be found occasionally; on the contrary you’d be hard pressed to find a Pizza Hut anywhere. As far as I can tell, there’s just two branches left in two major cities.