Hi,
how can I remove the sidebar in CPT single's page using DIVI theme?
I've tried to create a single-myCPT.php in the child theme, copied from divi theme, and delete the line <?php get_sidebar(); ?>, but it doesn't worked.
Are you using Toolset's Content Templates to create the template for your single custom posts?
If so, when editing the template without any blocks selected you'll find Theme Options settings in the sidebar where you can override the Divi theme settings and, in this case, specify that you want to use full-width layout without a sidebar.
(Note that Divi now also has its own templating system, but I don't know what is required to disable sidebars in that case, you would need to contact Divi support if you are using that.)