Don't eat granola bars! They're just as bad as as eating sweets, as they're full of sugar and pretty much all of them are UPF and full of palm fat and emulsifiers and artificial this, that and the other. They have little to no actual nutritional value.
Eat real food. So, if you feel you definitely need to eat a snack, make it a handful of nuts, or a piece of fruit.
Don't get too hung up on the calories. Think more about the quality of the food that you're eating. Avoid cakes, sweets, biscuits, crisps as much as possible. Fill up on vegetables, fish, chicken, beans and pulses.
One of the quickest meals I make is veggie chilli.
When you get home, boil some water in the kettle. Measure out some bulgur wheat into a bowl (enough for the two of you, according to appetite), pour boiling water over the bulgar, to cover it and a few centimeters above it and leave it for about 10-15 minutes to absorb the water.
Meanwhile, open a tin of kidney beans and a tin of black beans. Drain and rinse. Tip them into a shallow pan with a can or two of chopped tomatoes, a couple of handfuls of frozen peas and/or frozen sweetcorn and a blob of tomato paste. Add some garlic and some chilli powder, to taste. Heat and simmer until it reduces and thickens slightly.
Tip the bulgur into a sieve to remove any remaining water and then divide between two warmed pasta bowls. Spoon the chill on top.
It takes about 15 minutes from start to finish.
Alternatively, how about a vegetable traybake? Put the oven on to 180° Fan. Slice up one aubergine, one courgette, one onion and one pepper (any colour).
Line a large baking tray with a silicone sheet or with baking parchment. Chuck the veggies on the tray. Drizzle a generous slug of olive oil over it and mix it around with your hands, then spread it out.
Pop it in the oven for 20 minutes or so. In the meantime, open a can of chickpeas and rinse and drain. Put them in a bowl with some olive oil and your choice of spice or dried herbs . I quite like using harissa paste in mine, but you might prefer something else.
After the 20 minutes are up, take the tray out of the oven and add the chickpeas to it and mix them around. Put it back in the oven for approx 15-20 minutes.
In the meantime, make some peanut sauce. Using the bowl that had the chickpeas in, put two tablespoons of smooth peanut butter and a generous slug of soy sauce (maybe about a tablespoon. Mix with a whisk (not an electric one). Gradually add water while whisking, till you have a fairly runny mixture. Then add chilli powder or curry powder or ginger (whatever you want, to spice it up). Mix well. Microwave for 30 seconds, mix again.
When the veggies are cooked, remove tray from oven and serve the veggies and chickpeas into warmed bowls. Spoon over the peanut sauce and then scatter some mixed seeds on top.