I found this trick on Pinterest, one of my favorite websites.
To pack an apple for lunch without a) it turning brown or b) putting lemon or orange juice on it, you can use a rubber band!
Just make four cuts on the apple around the core. This will make eight apple slices and one square core in the middle.
Then just reassemble the apple (yours won’t have come apart as much as my exploded view above), and put a rubber band around it!
Good to go! I put mine in a bag, but in the future would probably just wrap it up in a napkin or something. It was still really nice by the end of the day when I ate it!