i’m a happy user of Amazfit Band 5. it’s dirt cheap, paired with gadgetbridge – works fine without sharing any data with cloud-hosted big brother, all in all – it helps to keep me moving around each day. i had few occasions when i needed to charge it [ every ~2 weeks ] and did not have original charger at hand.
this unsophisticated smart watch can be charged with cut in half USB 2.0 cable. pads at the bottom of the Amazfit Band 5 seems to have the following polarity:

USB 2.0 cables tend to have color scheme where black wire is GND, red – +5V:

with a bit of patience and cable holding – i can charge my band to ~30% in ~15min.

during my attempts of charging i’ve connected + and GND incorrectly more than once… still my band and charger survived.
Interesting!