In the nicest possible way OP - if I were you I’d find out the eligibility criteria first.
there’s a lot of misinformation circulating about disability benefits and what qualifies for an award of each of the disability benefits..
if you are awarded OIP, as pp says, you can spend it as you see fit.
No-one will ask if you could have spent money on raw ingredients rather than a pre-cooked meal, after you have been awarded it.
The requirements for PIP being awarded are around independent living - so for instance there are categories such as can you plan, prepare and cook a meal, can you plan a journey by yourself, dress yourself, wash yourself, take medication yourself etc.
Contrary to what a lot of people would have you believe it’s not purely diagnosis based awarded benefit but about how much assistance you need with daily basic tasks.
Many, many people will have illnesses that cause them pain, fatigue or insomnia etc but they can still wash, dress, feed themselves, take medication, travel (in terms of walking a certain distance and in terms of planning, budget, cook etc.
Best of luck