For years I had muesli but eventually realised I hate the stuff.
So now I have a light-weight, minimum-prep, easy to eat breakfast that works for me :
40g of (home) dehydrated fruit, rehydrated overnight - the remaining hydrate makes a good fruit drink, as well.
a couple of chocky nut bars - 70g
Coffee - 15g = 2 spoons of ground coffee in the cup, boiling water, stir, let it settle for a couple of minutes - so good - but don't drink the last mouthful!
The fruit is a mix of mango, pineapple, apple, stone fruits, kiwi, papaya, anything else that is in season when I'm dehydrating - shelf stable and keeps for 12+ months.