Endurance training can last between 3-4 hours, or longer. That challenge here is that, unlike a sports game, you can't be subbed out for a water break. Typically you are biking, running, or erging with little or no breaks. For such a long period of training or practice time, you body require carbohydrates for energy. Here are five things you need to think about when planning training snacks:
Food needs to be easy and quick to digest. This is something that is consumed while you are training, so you need that energy as soon as possible.
Food needs to be easy to carry with you. Unless you have someone else with you to feed you as needed, your snack need to be readily accessable. This might be individually wrapped energy bites, gels, bars, or fruit.
It should be something that you would eat on race day. Training is not only a time to test you race day plan and it also a time to experiment with your snacks. Some people can eat dried fruit and it works great for them, but for others it might not be enough. Find your favorite flavor.
Food needs to be something that you actually like. If you hate dates, then dont pack dates for your training. Try other dried fruit or maybe a flavored gel. I have cut up a peanutbutter sandwhich into tiny bite size pieces for long bike rides, which worked great for me but if you dont like peanutbutter than if might not be a great option for you.
Consider your source of carbohydrate: a single source, like glucose, can only be oxidized at rates of approximately 60 g/h. A combination of carbohydrates, like glucose and fructose, can be oxidation at a rate of slightly more than 100 g/h if large amounts of carbohydrate are consumed. This is most likely in the form of a sports drink.