I would send a letter via email and fedex sig required (no need to use outdated certified mail which is cumbersome) and make the following points:

(1) Request further details on the damage including time stamped photos or any other proof that you were responsible for alleged damage.

(2) Deny all liability and threaten to seek damages for violation of federal and state debt collection laws.

(3) Explicitly reference that you are copying Marriott Rewards and Marriott HQ to complain that you don't appreciate harassment for something that you have no knowledge of and no responsibility for.

Of course this assumes you have no idea what they are talking about. If the sink did overflow during your stay, that's another matter.

It does not need to be a long letter (one page max) but it does need to be in writing.

Wonder if this is another one-and-done post where OP never returns?