Whether you have a baby or not, I highly recommend a bottle cleaner for your home! I use this thing all the time for narrow cups, especially sippy cups and our travel water bottles. I have one where the little nipple brush for bottles folds out and I use it on anything narrow, like sippy cup spouts and also my teapot spout. Here's a pic of what I'm talking about. This is a nice one because the little brush pops in the end and there is a suction cup on it.
Photo from Babies R Us
If you shop for one, make sure you pick out the longest one you see (water bottles can be long) AND one that has the little brush with it (cheap ones don't have it). It shall make your dish cleaning easier!