Why can't she use the drinking fountain? Don't they send a box of snack stuff and then the teacher puts out the snacks every day for the whole class?
Her school doesn't do lunch for the kindergartners? I wouldn't like that. Kids that bring their lunch often sit and watch the rest of the class all eating the same thing and forget to even eat their own food. I've seen it happen a lot in the younger kids.
When all the kids bring their own lunch they all watch to see what the others have then they eventually, if given enough time, will eat part of their own lunch.
Just don't send more than 3 items. More is overwhelming. And don't send weird food, the other kids will make fun of her. If she only likes PB&J that's pretty normal. If you send a lot of special foods all the kids will stare at her food and then make fun of her.
Please just keep in mind that no one will be sitting with her and making her eat. She'll take a few bites then run off to play with her friends.
Easy foods like a half sandwich, cut up fruit in a cup or a yogurt in a tube, and a drink. She won't have time or the inclination to eat more than that.