maybe some of you acquired a 16oz. Customizable Tumbler from Starbucks. While removing the bottom cap, you can retrieve the insert and do whatever you want with it.
Let me just offer you a .psd template sized over a A4 spreadsheet for the 16oz. Starbucks Tumbler
Within the .psd file, you'll have the stroke and the Work Path for the frame. All what you need to do is put your elements (picture, text , whatever) inside, print out (do not scale), cut around and insert in the tumbler.
have fun !