My daughter has always done strange thing with her tongue. From the second she was born, she had been sticking it out. Now she is pulling on it. She even refuses to drink from a sippy cup.
Some children whose tongues protrude from their mouths do so because they have low muscle tone in their mouth, lips and jaw. Some children do have a large tongue (more rare). Some children have this condition due to an underlying diagnosis. Often tongue thrust can be addressed by a speech therapist who can provide exercises and strategies for your child to work on at home.
Children with tongue protrusion may have upper respiratory problems, which leads to mouth breathing and open mouth postures, so do address your concerns with your doctor first who may refer you to a cranio-facial doctor to rule out concerns. I would not worry about a sippy cup and would concentrate more on helping your daughter learn to drink from a straw cup or open cup, since a sippy cup is only going to promote more tongue protrusion (and discontinue to bottle). With sippy cups children often rest their tongues underneath the sippy spout, which actually promotes tongue protrusion. A cup with a straw encourages a more mature sucking pattern making the tongue retract in the mouth (and kids can’t suck from a straw when their tongue is out) and strengthens oral motor muscles.
Children with tongue protrusion often do have difficulty with speech and feeding, so I recommended also seeking the advice of a speech and language pathologist in your area as soon as possible.