Inter-sentence space without a period?

Set the space factor to the space factor code of the period.

\documentclass{article}

\newcommand{\intersentencespace}{\spacefactor\sfcode`. \space}

\begin{document}

Ends.\ Here.

Ends. Here.

.Ends\intersentencespace Here.

\bigskip

\xspaceskip=30pt

Ends.\ Here.

Ends. Here.

.Ends\intersentencespace Here.

\end{document}

The strange code .Ends\intersentencespace Here is for getting the same width before the space.

In the first three lines, the normal spacing is considered. In the second part, an artificially enlarged \xspacskip clearly shows the effect.

You can define your own command, by adding fontdimen2 (interword space) to fontdimen7 (extra space). See section 4.3.1 of TeX by Topic .

\documentclass{article}
\newdimen\mydimen
\mydimen=\fontdimen2\font
\advance\mydimen by \fontdimen7\font
\newcommand\sspc{\hskip\mydimen}
\begin{document}
\noindent
test. test\\
test\sspc{}test\\
test test
\end{document}