Energy bars and flapjacks can be a convenient snack between meals or a good pre/post workout snack for athletes; however, they should never be used to replace a meal. You can also get just as many calories, carbs, and protein from a good pre-workout snack such as a banana with peanut butter, apple with a handful of nuts. The important thing if consuming flapjacks or snacks is to check labels for sugar and carbohydrate content. The ideal is to have a low carb and high protein snacks.
Examples would be protein flapjack bars by Reflex. These have high protein and low carbohydrate content. Protein Plus Power bars is another good example of low carbohydrate and high protein content.
Other snack options would include:
Goji berries, coconut chips, pumpkin seeds, bounce balls, pulsin bars, hummus, or nut butters.
Palm full of nuts
Pot of natural yoghurt with some nuts and a handful of fresh berries.
Protein shake with full-fat yoghurt, nut butters and even healthy fats such as coconut oil or flaxseed oil.
2 to 4 squares of high-cocoa dark chocolate with some nuts.