\renewcommand{\thefigure}{A.\arabic{figure}} % redefine the command that creates the figure number; the new numbering scheme is now A.1, A.2, ...
\setcounter{figure}{0}  % reset counter
\renewcommand{\thetable}{A.\arabic{table}} % redefine the command that creates the table number; the new numbering scheme is now A.1, A.2, ...
\setcounter{table}{0}  % reset counter

\begin{sidewaystable}[!htbp]
\subsection*{A table or figure sideways}
	\centering\includegraphics[width=0.95\textheight]{example-image-c}
	\captionsetup{width=0.95\textheight}
	\caption{\small Exemple for a figure or table that is sideways with its caption below}
	\label{Atab:mysidetab}
\end{sidewaystable}

\begin{figure}[!ht]
\subsection*{A figure with subfigures}
    \centering
    \begin{subfigure}{0.49\textwidth}
        \includegraphics[width=\textwidth]{example-image-a}
        \captionsetup{width=0.9\textwidth}
        \caption{Caption for figure a}
        \label{Afig:41fig}
    \end{subfigure}%
    \begin{subfigure}{0.49\textwidth}
        \includegraphics[width=\textwidth]{example-image-b}
        \captionsetup{width=0.9\textwidth}
        \caption{Caption for figure b}
        \label{Afig:42fig}
    \end{subfigure}
    \hfill
    \centering
    \begin{subfigure}{0.5\textwidth}
        \includegraphics[width=\textwidth]{example-image-c}
        \captionsetup{width=0.95\textwidth}
        \caption{Caption for figure c}
        \label{Afig:43fig}
    \end{subfigure}%
    \begin{subfigure}{0.5\textwidth}
        \includegraphics[width=\textwidth]{example-image-a}
        \captionsetup{width=0.95\textwidth}
        \caption{Caption for figure a}
        \label{Afig:44fig}
    \end{subfigure}
    \caption{Caption for figures a, b, c, and a again}
    \label{Afig:4figs}
\end{figure}