Yes, because they help dislodge any leftover formula that becomes more difficult to remove if it’s caked on. In fact, it’s a good idea to rinse out baby bottles and go through them with a light bottle brush scrubbing if you wait a couple days to fill up the machine before you run it. It’s also good to have bottle scrubbers on hand when you travel, because you won’t be able to thoroughly wash bottles in hotel rooms without one, especially with no access to a dishwasher.;;