There is no weight at the bottom of the straw to make it non-spillable. Our Straw Training Cup has a leak-proof cap and we are spill-proof when fully shut. To minimize the chances of leaking, we engineered a pressure system to keep liquids inside the cup.
If you need help with a leaking cup, please review the troubleshooting steps in this article: My straw training cup is leaking. How can I fix this?