Your profile says you're 25. Barring a medical condition, you're perfectly capable of going without food for a day. In fact, doing so periodically is arguably good for you.
If you're worried about the scent and noise of eating in stand and don't want to fast, it's really hard to beat a thing of ensure. I pop the seal before I put it in my bag. That way all you have to do is open it and drink. Minimum of odor since the bottle is airtight. No noise. It's not gourmet, but it's calories if you need them.
I've also carried cheese sticks and they work well. Minimum of garbage, high in fat and protein, tasty, and quiet to eat. No real smell to them.
Fasting is just the easy solution to me.