If you bring a Brita filter water bottle empty, they will let you bring it in? Don't see anything about it on FAQ so not sure. Also riding my bike and will have a bike helmet I want to lock in rented locker...assuming not an issue?
We locked our bike helmets up with the bikes. They were there at the end of each night. I doubt they will prevent you from bringing it into the locker though. Water bottle should be fine as long as it is empty.
As a precaution, bring a small bike pump, or spare tires, at least to have at your house. We got a flat tire every night! Biking home on a flat sucks, especially against the wind. Buy good tires, that seal against thorns.