Couple of these on thingverse, none fit my standard sippy cups. Created this one from scratch in fusion 360.

To change it edit the sketch, from there you can increase or decrease the base circle for the cup side, or pull it farther away from the center if needed

 

Thank you for sharing ... looks like good work ... now to find a printer in my area ... or maybe there is a production-level printer out there to run a batch of them ...??

 

there's lots of pay to print places. Make sure you have it done in petg or asa

 

Nice design. Thanks for posting the file. I saw a recent posting and am considering printing one for my mini. I assume you print this right side up? Unless there is no bottom in either cup? In order to avoid supports how do you think it would work to move the large cup holder up so its bottom is flush with the bottom of the small one? My Mini is in storage for a couple more weeks and too far away to go check if this would have positive or negative consequences in use.

 

I print it with supports just like it's shown in the fusion 360 screenshot