In addition to my comment on your question, I installed a trial version of Visual Studio 2013 (Ultimate) and I can confirm that the space works to complete IntelliSense suggestions. Combining all the comments, it seems to work in the following versions:
Here is a screenshot of my IntelliSense settings located in Tools > Options > Text Editor > C/C++ > Advanced :

As a last resort, you can try changing all your settings to standard ones, as indicated in this answer :
Tools > Import and Export Settings > Reset all settings
UPDATE . After reading JoshC's comments, I experimented a bit more and I have a problem too. This seems to be related to whether the element you are trying to autocomplete is a member of a type or namespace. If this is (e.g. std::string ) then space will work. If this is not (for example, void ) then this will not work (but for some reason the tab will work). According to this link , you can manually call the "Participant List" function by pressing CTRL + J, and in this case on an empty line it will include elements that are in the global namespace, however this is clearly not a practical solution.
I have no idea why he distinguishes between space and tab in this way. If anyone knows of a workaround, please let me know and I will edit this answer again.
The following would seem to mean that there is no solution for C ++:
http://visualstudio.uservoice.com/forums/121579-visual-studio/suggestions/2656132-support-committed-by-pressing-the-space-bar-in-c
When using Visual Studios 2012 for coding in C ++, how do you autofill code in IntelliSense? (see comments)
Jbentley
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