A few days ago I opened a new milk carton and though that was kind of hard. So I brain stormed different ideas and this is what I came up with. I tested it and it works great.(this also might help kids with opening the milk too)

print settings

brim: 5mm

supports: none

speed: 50% for better bed adhesion 

infill: 10%

If there are any questions or remex ideas just comment there is also a step file to tweak the design.