I'm curious how people are marking their bottles to track which batch is in each. With 3 or 4 on the go, it's pretty easy to mix them up once they're in the fridge.
With glass bottles and crown caps, I've been using a sharpie to mark the cap. With PET bottles, different colour elastics around the necks because I reuse the caps, and don't want to mark them up.
Any other ideas?