Hi
Apple's Limited Warranty covers issues due to defects in materials and workmanship, but not due to accidental damage.
If you have previously purchased AppleCare+, then the issue may be covered as one of up to two claims for accidental damage, each of which is subject to a service fee / excess.
However, as the service fee for an AppleCare+ claim is significantly higher than the cost of just buying a replacement cable or USB Power Adapter, I suggest that you buy a new cable or Power Adapter (depending on your meaning) instead.
In the US, for example, the service fee is $69 vs a cable cost of $29 - $39 and a USB Power Adapter cost of $19:
- Apple Watch Magnetic Charging Cable (0.3m) - Apple
- Apple Watch Magnetic Charging Cable (1 m) - Apple
- Apple Watch Magnetic Charging Cable (2 m) - Apple
- Apple 5W USB Power Adapter - Apple
If buying a replacement, having warranty cover or AppleCare+ does not entitle you to any discounts on those prices.