The only option you have is to accept the return. Any other option you will lose the money and the bottles. DO NOT ask eBay to step in under any circumstances. As already mentioned, the second you ask them to step in, the buyer gets an immediate refund and gets to keep the item.

As others have said, send a postage label quick smart before the buyer asks eBay to step in. Otherwise, you will lose both.

Edit: it's unlikely eBay will remove that negative feedback. Best way to tackle that is to leave the buyer username in a polite reply. Something like "<username> claimed not as described due to me not providing tax invoice" or whatever fits into the space. Don't be rude in a reply, whatever you do!