After the initial sterilization (submerge in boiling water for five minutes), a thorough washing with hot, soapy water is all your bottles really need. If you're not confident in your cleansing skills, throw the bottles in the dishwasher on hot. Make sure to put caps and bottles in a basket. If your baby contracts thrush (an oral yeast infection somewhat common in breastfed babies), your pediatrician might tell you to sterilize all bottles, pacifiers and teethers between each use... Otherwise, don't bother.