What would be the best way to store JSON content with a node? Can I just use a text field for this or will this destroy the data?
I do not need to query this data, only load it occasionally.
I'm using Drupal 7 and MySQL 5.5.
Text fields can store JSON data since JSON, by definition, is a serialized format. This is provided the JSON data fits the size of your text field. If you go this route, you should make sure your field is validated for valid JSON before saving and is under your storage limits.
If you want something more versatile, you might want to add your own custom field with the Field API. There's also the JSON Field module, but it only has a D8 release.
As Sahwn said, JSON is simple text and you can store/read it in longtext field,(**Notice set html format to plain, maybe CKEDITOR cause unwanted results).
and finally according to my experiences if you JSON not minified try to minify it with some think like
(first add custom submit handler for your form and in submit handler minify it to minimize database memory used )
$form_state['yourfield_name'][0]['safe_value'] = preg_replace('/\s(?=([^"]*"[^"]*")*[^"]*$)/', '',$form_state['yourfield_name'][0]['safe_value']);