Label sippy cups with nail polish
Here's how Katie kept sippy cups identifiable:
Labeling supplies for preschool reminded me of when I needed to label sippy cups and bottles for daycare. Tape peels off, and while Sharpies last a while, on some plastics a while only seemed to be a couple of washings and then I was trying to figure out which of two identical cups was the one we brought. What I started doing instead was using fingernail polish. It's not the easiest thing to write with, but you can at least get initials on most things and it lasts a lot longer.