Why does my homemade kombucha always have a weird, sour taste after the first fermentation?

I totally get why you're frustrated with your homemade kombucha having a weird, sour taste after the first fermentation. I've been there too, and it's definitely not the refreshing drink you're aiming for. From what you've described, it sounds like you've already tried tweaking your recipe and brewing conditions, which is great. One thing you might want to consider is the pH level of your brew - if it's too low, it can give your kombucha that sour taste.

I'd recommend checking the pH level of your sweet tea before you add the SCOBY, and also after the first fermentation. You can use pH strips or a pH meter to get an accurate reading. Ideally, you want your sweet tea to have a pH between 4.5 and 5.5, and your fermented kombucha to have a pH between 2.5 and 3.5. If your pH levels are off, it could be affecting the flavor of your kombucha. As for your SCOBY, it's possible that it's just not healthy, but it's also possible that it's just adjusting to your brewing environment.

As for the health implications of consuming sour-tasting kombucha, I wouldn't be too concerned about it. Kombucha is generally considered safe to drink, even if it's a bit sour. That being said, if you're consistently getting a sour taste, it might be worth taking a closer look at your brewing conditions and SCOBY health to make sure everything is okay. To maintain a healthy SCOBY, I'd recommend making sure it's always covered in liquid, keeping it away from direct sunlight, and feeding it regularly with fresh sweet tea.

Lastly, I'd say don't give up on your homemade kombucha just yet! It can take a few batches to get the hang of it, and troubleshooting is all part of the process. If you're still having trouble, you could try reaching out to other kombucha brewers online or in person to see if they have any tips or advice to share. Good luck, and I hope you eventually get the smooth, refreshing taste you're looking for!