The 'quick and easy' commercial breakfasts you can buy are, in my opinion, universally disgusting. They seem to be full of artificial flavours and have a texture lacking all interest. They may be 'so simple' but are they what you need at the start of a day's walking?
This is a brilliant and simple porridge recipe that works superbly for the rehydration / cosy method. I nicked it off 'Captain Paranoia' (AKA Kevin the 'Squeezebox Stove' designer) but then I mucked around with it a bit:
50 gm porridge oats - the normal, cheap kind not the 'instant' variety
25 gm sultanas
10 gm dried fruit*
1 tsp milk powder
1 1/2 tsp sugar
1/8 tsp salt
Pinch of cinnamon
This will give you a dry weight of c. 100gm, store in a ziplock bag and mix contents well
Add 150-170 ml of boiling water to the bag, ensure contents are well-mixed (seal and shake) and put in cosy for 20 minutes.
You can make endless varieties of this recipe by using different fruits, brown or white sugar, try nutmeg instead of cinnamon, or add dehydrated honey broken into tiny pieces. Make a variety and take a selection with you on your trips.
*I use Sainsbury's 'Fruit Mix' which is about £1 for a small bag, it contains dates, mango, sultanas and other yummy stuff. You could substitute coconut flakes, dried apple slice, banana chips etc etc.