I opened one of those up to see what the cell was>tiny little lithium. 
Seems like ‘double trash’ (plastic +lithium) so someone can get a fix. 
Not a great replacement for cigarette butt/filter trash.
I put a short lead on it and use it to power an RC volt/amp tester I have that needs ancillary power below 4.0v. It’s main advantage is small and light vs a small NiMh pack.
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I found the a mix of those with aluminium casing with press fit plastic and all plastic construction.
One had USB-C charging and some segment display, I assume for power remaining. Surprising amount of electronics, I assume they’ve some counter for number of recharges before you have to buy a new one.
Good idea about assembling one with an external lead for low current demands …
You know you are addicted when… 
More-so as an excuse for the manufacturer to say you have to buy a new proprietary battery after e.g. 100 recharges.