The Codes set minimum standards for how you must be treated while detained. A cell should be adequately heated, lit, cleaned and ventilated, and you must be given enough bedding to be reasonably comfortable.
You must be offered at least two light meals and one main meal in any 24-hour period, plus drinks at meal times and on reasonable request between meals. Dietary and religious needs should be met where practicable.
In any 24-hour period you are entitled to a continuous period of at least eight hours' rest, normally at night, free from questioning, travel or interruption arising out of the investigation. Interviews should not normally take place during this rest period.
Breaks from interviewing should be made at recognised meal times and at intervals of around two hours. Your physical condition must be considered: if you are unwell or injured, appropriate medical help must be called, and that takes priority.
This is a plain-English summary. For the exact rules, read the official PACE Code C.