Minipage similar to full-width environment -- with nice spacing

fullwidth-minipage

\documentclass{tufte-handout}

%% Just draws a baseline grid on the page
\usepackage{pagegrid}
\pagegridsetup{
  top-left,
  step=\baselineskip,
  arrowlength=1pt,
}
% End baseline grid code

\makeatletter
\newlength{\fullwidthlength}
\AtBeginDocument{\setlength{\fullwidthlength}{\@tufte@fullwidth}}
\makeatother

\usepackage{lipsum}

\begin{document}

\lipsum[1]

\noindent
\begin{minipage}{\fullwidthlength}
    \strut
    \lipsum*[2]
    \strut
\end{minipage}

% The value for <width> above should make that paragraph identical this one
\begin{fullwidth}
    \lipsum*[2]
\end{fullwidth}\unskip\par% <-- added this to fix spacing after fullwidth environment

\lipsum*[3]

\clearpage

\end{document}