Apple recently issued a warning to Apple Watch owners about using fake or uncertified chargers.
Using a counterfeit charger may lead to problems like slow charging, repeated chimes, and reduced battery lifespan.
Legitimate Apple Watch chargers made by Apple are always white, with some having regulatory info on the cable.
Check for one of the following model numbers on the cable to ensure authenticity
Use your Mac to check the charger's authenticity by going to Apple menu > System Settings > General > About > System Report > USB.
Certified third-party chargers should have a "Made for Watch" badge with the Apple logo on their packaging.
Ensure your third-party charger's packaging has the "Made for Watch" badge; if not, consider returning it.