I guess glass or ceramic? But would that be too heavy for a baby to hold? Plastic might leech toxins, that is why someone might want something other than plastic. I have never seen anything but plastic and if you want the thingy in the lid that prevents spilling, I don't know how you'd get away from plastic.<br><br><img alt="" class="inlineimg" src="http://www.mothering.com/discussions/images/smilies/lurk.gif" style="border:0px solid;" title="lurk">:
I suggest doing without one. If it's the convenience of having somthing portable to bring out withyou, this suggestion will leave you a lot more plastic free options. They have really nice small stainess steel coffee mugs with screw on tops at some outdoor equiptment/ apparrel stores. We never used sippy cups.I let the babies have sips out of whatever cup or container that I was drinking out of.
We use a <a href="http://www.thermos.com/thermos/cfm/prodDetail.cfm?id=297" target="_blank">Thermos Funtainer</a> for our toddler. The pop-up straw is small enough to swallow so you might want to remove it. DD is still able to use it without that portion of the straw. It doesn't spill much unless she holds it upside down and shakes it purposefully trying to make it spill. This was the best alternative I could find.