It is not necessary to sterilize the bottle when the baby is 1yr+....washing the bottle, like other untensils, with detergent and tap water (if you believe it is as clean as the standard in Hong Kong) will do.
Don't think that it is always better to sterilize the bottles...if you make the eating wares or the environment "too" clean / germ free...you may affect your baby to establish a good immune system in his body......