M.W.
I started introducing the sippy cup to my, almost 8 month old, daughter around 6 1/2 months. I tried the playtex first sipster and she didn't do well with it. I tried the Nuby brand and she has done MUCH better with it. I think she was more open to the Nuby brand becuase it was more like the nipple of her bottle.She does better without handles. I give it to her at least one feeding a day for now. We had some set backs when her gums were really bothering her from teething. I'm hoping to have her fully transitioned by 9 months. Good Luck.