Whats the best whole milk but has to be lactose free for my 1 yr baby and that doesn't cause constipation? or all of them cause?

Lactaid is one : Brand name, but there are others. 16-21 oz./ day of milk & milk products is recommended. At that amount, constipation usually isn't a problem. A word about sippy cups-they keep the tongue forward in an immature suckling position. Since the same muscles used for drinking & eating are used for speech, an open-mouthed or " commuter" cup that promotes lip closure is preferable.