Undefined control sequence. \end{frame} problem with algorithm in beamer

After adding \end{document} and [fragile] the error message in your MWE tells that \subitem is undefined. To solve this problem, define it to do whatever the output should look like - in the following I used

\newcommand{\subitem}{\par\qquad}

but you can change this according to your needs.

There are some superfluous packages in your example: you don't need graphicx or xcolor with beamer, as beamer already provides this functionality.

\documentclass{beamer}
\usepackage{etex}
\usetheme{Warsaw}
\setbeamercolor {alerted text} {fg=blue}
\logo{\includegraphics[height=.8cm]{example-image}}
\usepackage{beamerthemeshadow}
\usepackage{textcomp}
\usecolortheme[RGB={0,153,0}]{structure}
\usecolortheme{crane}
\useinnertheme{rounded}
%\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{verbatim,longtable}
\hypersetup{pdfpagemode=FullScreen}
\usepackage{verbatim}
\usepackage{pdflscape}
\usepackage{booktabs}
\usepackage{multirow}
\usepackage{array,colortbl}
%\usepackage{xcolor}

\usepackage{ragged2e}
\usepackage{algorithm}
\usepackage{algorithmic}
\usepackage{subfig}
\newcommand\Fontvi{\fontsize{6}{7.2}\selectfont}
\setbeamertemplate{caption}[numbered]
\setbeamertemplate{frametitle continuation}{}
\usepackage{adjustbox}
\definecolor{deepblue}{RGB}{0,0,128}

\newcommand{\subitem}{\par\qquad}

\begin{document}
\begin{frame}[fragile]
 \begin{algorithm}[H]
    \caption{Algorithm }\label{alg:alg1}
    \begin{algorithmic}[1]
        \STATE Sink node  
        \STATE Store the value 
        \subitem a\textunderscore value .
        \subitem c\textunderscore value .
        \subitem SINR\textunderscore = .
        \subitem kappa\textunderscore = .
        \STATE Sink node broadcasts 
        \STATE Each .
        \STATE .
    \end{algorithmic}
 \end{algorithm}
\end{frame}
\end{document}