My DS loves to drink from a normal cup, but like yours, cant be trusted, and I only give him a couple of mm in the bottom at a time... And he only get it in his high chair, or when we are out, and he will sip from my cup, with me holding it.... My FDC told me he was interested in the cup after watching the older kids with it, and so I tried him out and it seemed to work. We just use a smallish plastic cup from my picnic set...

We have a sipppy cup that is like a real cup, but sealed, and ds loves that. I got it from fluffylimes store... It is good, in that he can lug it around, but no spills... unless it falls on its side for an extended period and a little leaks out, but it is generally good.