For snacks, nothing like fruit. Pineapple, mango, organic Bananas, apples and such. But ... too much can leave me unbalanced...... so I sometimes eat unsweetened coconut too. You can take some in a small bag with you anywhere you go.
Alternatively ...unsweetened dried coconut and organic dried apricots make for an awesome high energy snack. The coconut stabilizes the blood sugar . This is very tasty. The organic dried apricots have a totally different taste(real) than the crappy orange gummy bear tasting ones you find preserved with sulfur.
Or add some some nuts .... walnuts, pecans or pumpkin seeds.