I love my Costco Takeya hydroflask! I just don't like choking on ice cubes when they make there way though the mouthpiece. I designed this little strainer that press fits into the cap. I printed in flexible TPU which allows it to fit snugly in place. It would possibly work with PETG which has a little bit of flex to it (and its also food safe).
The diameter is 50mm so it may fit in other brands of bottles.
yoyi TPU or PETG
If printing with TPU, don't use supports. You can use supports with PETG.