Latex "element of with two strokes" (⋹)

Here's one option using \ooalign:

\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}

\newcommand\Inn{%
  \mathrel{\ooalign{$\subset$\cr\hfil\scalebox{0.8}[1]{$=$}\hfil\cr}}%
}
\begin{document}

\[
A\in B
\]

\[
A\Inn B
\]

\end{document}

The result:

And if you need it for the different math styles:

\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}

\newcommand\Inn{%
  \mathrel{\mathchoice
    {\ooalign{$\displaystyle\subset$\cr\hfil\scalebox{0.8}[1]{$=$}\hfil\cr}}%
    {\ooalign{$\textstyle\subset$\cr\hfil\scalebox{0.8}[1]{$\textstyle=$}\hfil\cr}}%
    {\ooalign{$\scriptstyle\subset$\cr\hfil\scalebox{0.8}[1]{$\scriptstyle=$}\hfil\cr}}%
    {\ooalign{$\scriptscriptstyle\subset$\cr\hfil\scalebox{0.8}[1]{$\scriptscriptstyle=$}\hfil\cr}}%
    }%
}

\begin{document}

\[
A\in B\quad{\textstyle A\in B}\quad  L_{A\in B}\quad  M_{L_{A\in B}}
\]

\[
A\Inn B\quad{\textstyle A\Inn B}\quad  L_{A\Inn B}\quad M_{L_{A\Inn B}}
\]

\end{document}

It's Unicode symbol U+22F9 "Element of with two horizontal strokes": ⋹.

When LuaTeX or XeTeX is used, then the symbol is available with the following fonts:

• Asana Math

  \documentclass{article}
  \usepackage{unicode-math}
  \setmathfont{Asana-Math.otf}
  
  \begin{document}
  \[ A \isinE B \]
  \end{document}
  

  

• XITS Math

  \setmathfont{xits-math.otf}
  

  

• The Latin Modern Math or TeX Gyre Math fonts do not have the symbol.

This uses a stack, and will work in all mathstyles.

\documentclass{article}
\usepackage{graphicx,stackengine,scalerel}
\usepackage{amsmath}
\newcommand\Inn{\def\stackalignment{c}\def\stacktype{L}\ThisStyle{\mathrel{%
  \stackon[0pt]{$\SavedStyle\subset$}{\scalebox{0.86}[1]{$\SavedStyle=$}}}}%
}
\begin{document}

\[
A\in B
\]

\[
A\Inn B\quad
\scriptstyle A\Inn B\quad
\scriptscriptstyle A\Inn B
\]
\end{document}