Most pediatricians recommend that a child be weaned off the bottle by 12 months old.
There are a couple of reasons for this. One is tooth decay. Any liquid that has prolonged contact with the teeth other than water can cause the teeth to decay. This includes: formula, milk, juice, soft drinks, sugared drinks, etc. A child falling asleep with a bottle in their mouths can cause this to happen.
Another reason is ear infections. A baby that is drinking while lying down can cause the liquid from the bottle to go up a small tube leading to the middle ear, causing middle ear fluid.
So it truly is in your child's best interest to get them off the bottle and using a sippy cup as soon as possible.
What Kind Of Cup To Buy:
Buy a sippy cup that has a rubber tip as opposed to the hard plastic because it will feel very similar to a bottle and will make the transition easier at first.
Be sure that the cup is spill proof and has a valve to fit in the cup that you can use when you want to prevent the cup from leaking while it is in the diaper bag, stroller, car, etc..
The Gradual Transition Method:
Introduce the cup at meal times and let it be the only option that they are allowed to use while eating. Have your child take a couple of bites and food and then give them the cup to drink with. You can try gently putting the cup to their lips and tilting until they start to get the idea of how it works.
Let them play with it and get used to the feel of it.
Switch all of their favorite beverages to the sippy cup and only put water in their baby bottles. This way they start to look forward to the cup for their milk and favorite juices and the bottle starts to lose interest for them.
Eventually let them use the cup at snack time as well. Introduce a great new drink they may not have tried before such as chocolate milk so they are focused more on the beverage than the container holding it.
Start eliminating the bottles from the afternoon naps. Give them the cup before they go to sleep and when they wake up.
Start making the sippy cup the only option when going out places. They will quickly realize that it is the cup or nothing. Make sure at this point that the bottle is no longer an option at any other time except bedtime.
Eventually try the nap trick at night as well. Give them the cup before they go to bed and as soon as they get up, but no bottle.
The Cold Turkey Method:
If you would rather just try to eliminate the bottle in one fell swoop you can try the Cold Turkey method.
The best way to go about this is to give your child about a weeks notice ahead of time. You can do a fun calendar countdown to the day they will get their first Big Boy Cup or Big Girl Cup Each time you give them the bottle remind them that they only have a few more days to the Big Boy Cup day! Make it sound fun and exciting.
Bring them to the store and let them pick out their new sippy cups themselves.
Put it someplace where they can see it everyday and keep reminding them Only a few more days!
The day before, have them help you collect all of their bottles and put them in a garbage bag together. (Save one and hide it just in case transition is harder than you anticipate.)
Make a big production of the two of you taking the garbage bag to the garbage can and that is it time to say Bye-bye to the baby bottles and to say Hello to the new grown-up cups.
Do your best to stick to keeping that hidden bottle in the back of the closet never to be seen again!