I made this instructable to go with some bottles I sell on ebay
for adult babies. It could also be used for adults with special needs and even pets. This tutorial was made for Nuk style orthodontic nipples but the method will work for any latex nipple (not sure about silicone, haven't tested it but let me know if you do and it works!).
I know all you AB's have experienced this at one point. You're trying to drink from your bottles only to find that your getting almost nothing out of them. You try to cut the hole in the nipple a bit bigger but the knife just won't go through. You push it in a bit harder only to slice the whole nipple apart (and your finger...ouch!) and completely wreck it. After having gone through too many nipples this way myself, I decided to play around a little and have discovered a method that works perfectly.