The Capillary Cup is a zero-gravity cup designed by NASA astronaut Donald Pettit on the International Space Station. The product is an open drinking cup designed to be used in a microgravity environment, developed from Pettit’s desire to drink water without a bag and straw in outer space.
Because there’s no upsidedown in space. A sippy cup works by using gravity, you have to turn the cup upsidedown to get the liquid to go to the sippy spout so you can suck it out. In outer space the liquid would just be floating free inside the sippy cup and not near the spout for you to suck it out.
They make sippy cups with straws, it has a little thing that goes all the way down to the bottom and like a soft silicone straw built-in to the top.
But the whole premise of this device is that the person didn’t want to drink from something straw-like. Which a sippy cup is to begin with.