custom field in sidebar

I am trying to implement custom field values from various posts (event calendar posts) into a sidebar link. Basically I need to do it in a PHP method where I call for the keys. I started using the plugin get_all_meta which works great, but the problem is that it makes an array with a new key (0, 1, 2) for each array value.

What I need to do is connect a post ID (I can already get that) to a custom field key’s post ID and then get that custom field value. Any suggestions/help with how to go about doing this? I tried some ideas from the docs but nothing worked…