Without knowing which plugin(s) you're concerned with, here's some code that would get, set and clear a cache for a given item.
$output = '';
$cache = JFactory::getCache('com_something', '');
$cache->setCaching(true);
$cache->setLifeTime(86400);
// See All cached items
echo "<pre>".print_r($cache->getAll(), true)."</pre>";
// Create a Cache ID that works for you :
$cacheid = md5('something'.JFactory::getUser()->id); // Just an example
// Remove cached output
//$cache->remove($cacheid);
// Get cached output
$output = $cache->get($cacheid);
if (empty($output)) {
$output = "something I want to cache";
$cache->store($output, $cacheid);
}
Using the docs at JCache, and echoing the current catched items with $cache->getAll() will look something like this to identify which item(s) you're interested in:
Array
(
[com_something] => JCacheStorageHelper Object
(
[group] => com_something
[size] => 0.09
[count] => 2
)
[Gantry] => JCacheStorageHelper Object
(
[group] => Gantry
[size] => 332.58
[count] => 5
)
[GantryLess] => JCacheStorageHelper Object
(
[group] => GantryLess
[size] => 354.04
[count] => 9
)
[myplugin] => JCacheStorageHelper Object
(
[group] => myplugin
[size] => 0.09
[count] => 2
)
)