Edit on 13-Jan-2016
I found another easy way to fix this problem. You can toggle the menu with a keyboard shortcut. You can read more about that in this blog post of mine.

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It has been a very long wait to get the "Hide Menu" feature in Linux versions of Sublime Text 3. Finally it was released. But the problem is, if it hidden once, there is no straight forward way to get the Menu back. I tried F10, Alt etc etc and nothing worked. So, I am sharing the trick which worked for me in this post.

It is simple. Close the Sublime Text 3, if it is open. Open

~/.config/sublime-text-3/Local/Session.sublime_session

in any of your favorite editors and then make sure that, "menu_visible" is "true" in all places in that file.

"menu_visible": true,

Thats it :) Open Sublime Text 3 now and ta-da... Menu is back :)

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Edit On Jan 10 - 2016

As I was doing the same task more often, I decided that put that in a script, like this

export FILE=/home/thefourtheye/.config/sublime-text-3/Local/Session.sublime_session
export TEMP_FILE=/home/thefourtheye/.config/sublime-text-3/Local/Session.sublime_session.bkp
sed -e 's/"menu_visible": false/"menu_visible": true/g' $FILE > $TEMP_FILE
mv $TEMP_FILE FILE

and then I added that to my shell script's rc file as an alias like this

alias sublime_fix_menu=~/.sublime_fix_menu.zsh

That's it :-) Now, I just have to close Sublime Text 3, type sublime_fix_menu in the shell, open Sublime again :-)