A lot of the sippy cups out on the market have soft spouts now. I like the Nuby brand sippys as they are really inexpensive, leak proof and easily found in your local walmart. I don't think a child that young should be taken off formula, there is so much packed in the formula now, even the DHA that is found in breast milk...I don't think a supplement has that, also a lot of vtamins are not absorbed the way they should be so that they provide the nutrition they claim.
Good luck
The straw cups work well too!
( and even though I know probably 90% are guilty of it we really aren't supposed to put them down to sleep with a bottle anyway, babys are meant to be held while bottle fed, but I openly and with out guilt admit that at some point each of my babies went to bed with a bottle of formula or milk occassionally!)