I own both a S’well bottle (which I hate because the opening is so small that I cannot fit the ice cubes that my freezer automatically makes through the hole) and The Coldest Water bottle. You have to shove this bottle brush into the S’well bottle. I tried to shove it in and with half of the head of the bristles in, I pulled it out. I didn’t want to damage the bristles which easily fit into the Coldest Water Bottle. OK. My husband and I just literally double checked both bottles with the brush and I think the S’well bottle opening is too small for the Coldest Water bottle brush. I didn’t want you to think I was prejudiced against S’well. I just think a smaller bristle brush will suit your needs better.