Take N Toss straw cups are great for teaching kids how to drink from a straw. You can give the cup a little squeeze and some of the liquid will come up through the straw. It is not completely spill proof, but usually only a little will spill out if it gets tipped over. They are light weight and easy for little hands to hold as well.

This cup is a great way to start teaching children to drink from an open cup with potentially less spilling than with an open cup. You can allow them to have some independence without worrying about the entire drink spilling right away if the cup tips over.
The cup has a round piece that fits down inside the cup above the liquid. It has small spaces all around the edge of the round piece that will allow liquid to easily flow out when the cup is tipped up. However, the entire amount of liquid will not pour out at once. It will flow through the spaces into a smaller stream for drinking with a more controlled flow than with just an open cup.