You talk about sneaking it in, so I assume you don’t have a lunchroom or fridge. Otherwise, you just put your snacks in the fridge with your bag lunch and who would know the difference?
Breakfast or energy bars. Nutri-Grain, Luna Bars, Clif Bars, etc. I think I’d lean toward the more calorie dense versions if you have little time.
Fruit. A bag of grapes, cut up apple. Dried fruits like apricots, dates, raisins.
Half a sandwich. PB&J or something that won’t spoil.
Re: snacks — a bag of nuts & some string cheese. But if this starts your eating window (raises insulin) you may as well just wait another hour. This sounds counter intuitive but to stave off hunger, chose a shorter fasting window. You might have to just power through it the first two days; start on a weekend. It’s tough to become fat adapted and reset your body into understanding how to burn fat as fuel if it never has to in the first place- and with 14:10, unless you’re doing keto it doesn’t need to, there’s always glucose available.