You can use \cvlistdoubleitem{Reading}{Athletics}
to have Reading in one column and the Athletics in the other. Languages are better be left alone as the current format is more descriptive IMO.
Code:
\documentclass[11pt,a4paper,sans]{moderncv} % Font sizes: 10, 11, or 12; paper sizes: a4paper, letterpaper, a5paper, legalpaper, executivepaper or landscape; font families: sans or roman
\moderncvstyle{classic} % CV theme - options include: 'casual' (default), 'classic', 'oldstyle' and 'banking'
\moderncvcolor{orange} % CV color - options include: 'blue' (default), 'orange', 'green', 'red', 'purple', 'grey' and 'black'
\usepackage{csquotes}
\usepackage[margin=.9in,scale=0.75]{geometry} % Reduce document margins-- ,scale=0.75
\setlength{\hintscolumnwidth}{3cm} % Uncomment to change the width of the dates column
\setlength{\makecvtitlenamewidth}{10cm} % For the 'classic' style, uncomment to adjust the width of the space allocated to your name
%----------------------------------------------------------------------------------------
% NAME AND CONTACT INFORMATION SECTION
%----------------------------------------------------------------------------------------
\firstname{Harish} % Your first name
\familyname{Kumar} % Your last name
% All information in this block is optional, comment out any lines you don't need
\title{Curriculum Vitae}
%----------------------------------------------------------------------------------------
\begin{document}
%----------------------------------------------------------------------------------------
% LANGUAGES SECTION
%----------------------------------------------------------------------------------------
\section{Languages}
\cvitemwithcomment{Tulu}{Mother tongue}{}
\cvitemwithcomment{Kannada}{Advanced}{Read, Write and Conversationally fluent}
\cvitemwithcomment{English}{Advanced}{Read, Write and Conversationally fluent}
\cvitemwithcomment{Hindi}{Advanced}{Read, Write and Conversationally fluent}
\cvitemwithcomment{Sanskrit}{Advanced}{Read, Write and Conversationally fluent}
\cvitemwithcomment{Konkani}{Basic}{Conversationally fluent}
%----------------------------------------------------------------------------------------
% INTERESTS SECTION
%----------------------------------------------------------------------------------------
\section{Interests}
\renewcommand{\listitemsymbol}{-~} % Changes the symbol used for lists
\cvlistdoubleitem{\href{http://tex.stackexchange.com/users/11232/harish-kumar}{TeX.SX}}{Chess}
\cvlistdoubleitem{Reading}{Athletics}
\cvlistdoubleitem{Yoga}{Pranayama}
\cvlistdoubleitem{Meditation}{Eating}
\cvlistitem{Not sleeping} %% This will give only one column
%----------------------------------------------------------------------------------------
\end{document}

\usepackage{multicol}
...\begin{multicols}{2}\section{...}...\end{multicols}
?\cvlistdoubleitem{Reading}{Athletics}
then you will haveReading
in one column and theAthletics
in the other.