Thanks so much for your feedback! We're always looking for ways to improve our chiller and its accessories, and we really appreciate you letting us know your thoughts.
One quick tip: make sure you're pushing down firmly on the sipper lid, it should suction onto the inner chamber really well. While it's not 100% leak-proof, it shouldn't gush liquid anywhere or create a big mess. If you're still having trouble after making sure the lid is fully seated, please reach out to us directly at info@cereschill.com, we are always happy to help!