How do I get to Snowdin before I fight Undyne the Undying?

I would like to go back to Snowdin to get cinnabuns for the Undyne fight in the Waterfalls. Since I'm playing Genocide, the duck that lets you cross the water and the ferryman are gone. Is there any way to go back to Snowdin?

Solution 1:

There is no way back to Snowdin without the duck or the ferry.

However, you can travel back to Gerson and buy Crab Apples. You still have to pay and they only heal 18hp but they're better than nothing.

Solution 2:

You can't. You have to restart the route and get them from there or use the cloudy glasses and crab from Gerson because even on a Genocide run, Gerson is still at his shop.