Sweet Potato Fly

by lydia on May 18, 2011

I love to experiment with new things in the kitchen, especially new ferments. Even better yet are fun ferments that my kids will actually enjoy. I have been inspired a ton by Sandor Katz’s awesome book, ‘Wild Fermentation’. If you don’t have a copy yet, you must get one. He sure did some serious experimenting over the years and I myself have gleaned from his experience. I can’t quite say what it was about this particular recipe that inspired me to try it. I suppose I thought a sweet beverage would be enticing enough for the kids since I eagerly desire for them to get more probiotics and enzymes into their diets. It’s not easy! They want sweet, so not all the fermented veggies go over too well. Kombucha takes several weeks to brew and is not always on hand, so I thought I give a fermented soda a try. This sweet potato fly, aka soda,  is slightly effervescent, fizzy and aromatically spiced. I tried this recipe ages ago and my kids have begged me ever since to make it again. I finally got around to making it again with a few slight tweaks from the original recipe. For a less unique spiced beverage, omit using the mace. My kids like it a bit better that way.

Sweet Potato Fly
Recipe type: Beverage
Serves: 1 Gallon
  • 1 teaspoon powdered mace (optional)
  • 2 large sweet potatoes
  • 1 to 2 cups sugar
  • ½ cup whey
  • 2 lemons
  • cinnamon
  • nutmeg
  • A few cleaned eggshells
  1. If using the mace, boil one cup water with the mace.
  2. Remove from heat and allow to cool.
  3. Grate the sweet potatoes and rinse well through a strainer to remove starch.
  4. In a large bowl, combine the grated sweet potatoes, 1 gallon water, sugar, whey, the juice and grated peel of the lemons, and a pinch of nutmeg and cinnamon.
  5. Crush the cleaned eggshell into the mixture.
  6. Add the cooled boiled mace.
  7. Stir, cover to keep flies and dust out and leave in a warm spot to ferment for about 3 days.
  8. Strain into a jug, bottles or jars, and allow to second ferment for a day or two to acquire a bit more fizz before refrigerating.
  9. Enjoy!

(cover photo credit; above photo – sweet potato fly while it’s fermenting)



  Subscribe to Divine Health
  From The Inside Out

We hate spam more than you do,
and we don't do it.

Join our weekly newsletter and get
our 52 Healthy Habits to Take Care
of Your Body FREE!



Val July 28, 2011 at 10:53 pm

You go on and on about how bad sugar is, and then this recipe calls for 2 cups. Practice what you preach

lydia August 4, 2011 at 1:10 pm

Hi Val,

First of all, you are right I do not like to use much sugar and I do believe it is detrimental to our health – this is a recipe that I do not make very often at all, and you will not find any other recipe on this site with this amount of sugar. Second of all. this is a fermented food, when you ferment things the sugar content is drastically reduced, not to mention the probiotics and enzymes help curb sugar cravings, so even though the sugar is reduced quite a bit, you still won’t crave or drink too much of the beverage. It’s considered a special rare occasion treat in our home and is a FAR better option than any sugar laden beverage on any store shelf!

Melinda September 12, 2012 at 3:38 am

Hi Lydia, do the eggshells add flavour or is there another purpose for having them in this? It’s an unusual ingredient.

Melody December 24, 2012 at 12:59 am

According to the Wild Fermentation book, the eggshells are alkaline and help temper the pH.

Hilary January 22, 2013 at 8:16 pm

I like the recipe! You are correct when it comes to this sort of thing, sugar is actually required to get the proper type of fermentation. Do you ever use the potatoes for anything or just the juice?

lydia February 3, 2013 at 9:26 am

I have never used the potatoes for anything, I suppose you could. I just compost them.

Deb February 19, 2013 at 9:21 pm

I just tried our first batch of this (1st ferment only) we strained it and the liquid was pretty viscous – is that right? It was not a thin beverage like kombucha. It also did not have any fizz – will that only occur after a second ferment? Does the taste change appreciably after a second ferment or refrigeration. I love my kombucha but this stuff is a little iffy for me – I want to love it…

lydia February 20, 2013 at 10:18 am

Yes the second ferment should help – and letting it second ferment in the fridge longer should help even more. This beverage I consider more of a treat and don’t make it often. Kombucha and water kefir are our mainstay fermented beverages around here.

Bea March 24, 2013 at 10:20 pm

I tried to make this 2 times last fall and it too was, as Deb stated, viscous. I threw it out because I thought I had done something wrong, now I am not so sure. I fermented it in an cloth covered crock. Would that cause the thickining? I noticed in your photo above a glass jar with a lid. I will try that next. Do you have any other thoughts? Thanks so much!! I too enjoy the “Wild Fermentation” book!!

lynna July 21, 2013 at 2:19 pm

Hello ~
My sister recommended I check out your kvass recipe and while I was cruising around I felt a kindred connection to all of you fellow sweet potato fly adventurers! I wanted to weigh in that my fly always comes out thick and creamy and we really enjoy it that way. Yum! Now to discover how to make a kvass the family will love ~ I am excited to try your version!

Deborah February 2, 2016 at 4:28 am

So…I forgot to rinse the potatoes off to remove the starch. Should I start over?

Comments on this entry are closed.

{ 1 trackback }

Previous post:

Next post: