A while ago I got into the habit of keeping snacks in my classroom in a big plastic (dark, non see-through mouse resistant) tub. I like to keep, graham crackers, pretzels, cheddar bunnies, Newman cookies, CheezIts, cereal, etc. It seems to be an incentive for kids to come in for tutoring at the end of the day, or at least to have them stave off their hunger (or ruin their appetite for dinner) as they're getting extra math help. I found that baby wipes and extra napkins and maybe small paper cups for pouring treats into are helpful.
There have been some incidents. Once during first period, a student mentioned she hadn't had breakfast and wondered if she could have a snack. I said sure, and envisioned her quickly taking something, closing the tub, and getting back to work. After I continue with my lesson, I glance over at her, and there she is in all her glory, open tub next to her, and an array of snacks on her desk. We quickly fixed that, and I made a mental note: no "tub" during class time.
Another time a student asked (during class) to have a snack. I said, no, that it was only for after school. Then she tries on her pleading voice, "but I really like them, pleaaaaaaasssssse". Ew. No means no. I'm reminded of a TV talk show I once saw where the message was, just because someone asks for something nicely, it doesn't mean you should give it to them, their example was: "oh I LOVE your diamond necklace. It's so beautiful and elegant. Can I please have it?"
Then there are the "vacuum" kids after school - not many of them, but, sheesh. All snacks inhaled, and thank you very much.
But mostly it has been something I think I'll continue.