How do I delete a vote (e.g.rate module)? Is there a module with a functionality to delete votes using the voting api? If not, how do I implement a button that erases all votes? Or is it easier if I just empty the MYSQL table?
The voting api defines some drush commands:

drush generate-votes &lt;entity_type&gt; &lt;vote_type&gt;
drush votingapi-recalculate &lt;entity_type&gt;
drush votingapi-flush &lt;entity_type&gt;


if you don't use drush, you can run the code from the function that the module uses on devel php or similar

&lt;?php
$entity_type = "name_of_the_entity";
$cache = db_delete('votingapi_cache');
$votes = db_delete('votingapi_vote');

if (!empty($entity_type)) {
  $cache-&gt;condition('entity_type', $entity_type);
  $votes-&gt;condition('entity_type', $entity_type);
}
if (!empty($entity_id)) {
  $cache-&gt;condition('entity_id', $entity_id);
  $votes-&gt;condition('entity_id', $entity_id);
}

$cache-&gt;execute();
$votes-&gt;execute();