The watered down vinegar (larger ratio of water) is the rabbit-safe cleaner a lot of people use. If you rinse thoroughly, the scent shouldn’t be left behind. He won’t get sick from exposure to vinegar smell though— Wick smells it all the time, as do I when I clean.
Apple cider vinegar is still acidic, so potentially. I’d spend a lot of time with either vinegars, because green growth is worriesome and you definitely don’t want any of that in the bottle.
In the future (unsure of your practices), I always dump and rinse out Wick’s bottle daily— I never just refill it. He doesn’t use a bottle anymore though.
I highly recommend replacing the bottle with a water dish instead. It’s much easier to clean and it’s easier for rabbits to drink out of = They will drink more water.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.