Straw keeps falling out

Sometimes the straw can be pushed too far into the silicone adaptor, which causes the silicone adaptor to not stay in place. Please try the following steps:

1. Remove the straw and grey silicone adaptor from the cap.
2. Remove the straw from the silicone adaptor.
3. Insert the silicone adaptor into the cap, be sure to press on the "wings" to the side of the adaptor and listen for an audible "click" once it is inserted into the mouthpiece of the cap. 
4. Gently insert the straw into the silicone adaptor.

Here is the video that shows how to install everything correctly. You might find it helpful!