I've successfully made homemade kefir, and I've already finished half the quart. I sweetened it with monk fruit, which I learned about from my experience with Bob's Red Mill's vegan protein powder, it doesn't have any calories and tastes exactly like sugar, from what I can tell, you might be able to notice a difference, but I would doubt it.
This is so simple to make. I could've planned it a little better, but I made it at about 1:00 pm, checked it before bed and them put it in the fridge around 8:30 in the morning. Mine is made with almond milk so it's not super thick like you'd expect kefir to be, but it is a little tart and definitely sweet. On this one I put aside about 1/3 cup for my next starter. It recommends you save 1/4 cup at the end of your batch, but I separated it early on because I may not want it to all be strawberry flavored.
This is super simple to make. I used a starter kit from Cultures for Health. I've seen people use plain old probiotics to start yogurt, like this one from Minimalist Baker. I haven't done it, but it definitely looks like it's worth a shot.
Here's what you'll need
1 quart or 4 cups almond milk - I used Califa Unsweetened
1/3 cup monk fruit sweetener
1 cup sliced fresh strawberries
Kefir starter - I used Cultures for Health
Coffee filter or cheesecloth + rubber band
Quart sized container - I used these, which turned out to be a good choice, because I can save my next starter in the smaller size.
Mix your kefir starter with almond milk
Place cheesecloth or coffee filter over the top secured with a rubber band. Leave 12-18 hours. Mine was there for about 20 1/2 hours and it was fine. Ideally, it should be at about 75° while it's culturing.
Remove cheesecloth and set aside 1/4 cup of plain kefir mix to use for your next batch and store in the fridge
Blend kefir with strawberries and monk fruit
Strain pulp through sieve and wash your original container if you're going to use it again
Store in fridge for up to 3 weeks