These are the rules concerning portable food:

The total amount of sold healing per reset must not exceed 3000 hp.
A maximum of 200 hp may be sold to one customer per reset. The cost
of such healing is calculated using this formula:

x = The amount of healing sold.

Cost = 4*x + x^2/10

This means that the more healing an item contains, the more expensive 
it gets. These items must have a weight of at least 1.

The "strength" of the food is equal to the amount of healing it makes to 
the player when he eats it. Typically this strength should not exceed 50.

Use the file "obj/food" for cloning and inherting purposes. Please read 
the file find out which functions to call.

Examples of food and drink and an inn selling these items can be found in
/doc/examples/apple_juice.c, /doc/examples/apple_cider.c and
/doc/examples/inn.c . Type "goto /doc/examples/inn" just to visit it.