Simple sushi and
Vietnamese spring rolls would be my personal choice, I've done that before.
You just eat them cold with some dipping sauce.
The preparation takes some time but actually making them is rather quick.
You don't have to use fish with the sushi, in practicality you can use almost any kind of meat.
There's a whole bunch of pre-made dipping sauces you can buy.
The good thing about all this is that you can vary the ingredients, so you get different flavours.
Using different sauces also adds some variety.
Other favourites:
* cured herring or some other canned or smoked fish (mackerel ... ) + some nice bread
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Noodle salad = cold noodles with peanut sauce and whatever protein, vegetable and salad you have
making peanut sauce is quick and easy, you could use a spicy sauce as well * pre-made Gazpacho soup + some nice bread [simply store the soup in a Tupperware container]
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instant-noodle salad As a uni student I just spread some Vegemite, or Marmite, on some flatbread.
I recommend varying things up. Eating the same thing over and over gets boring, unless it's pizza.
Hey ...
cold pizza, not that bad actually. Just cook it the day before and eat it with some rucola (rocket) leaves.