Create the table in Google Drawings and share it, either publicly or to anyone with the link and copy the sharing link.
Use the embed URL function or upload the Drawing to your Drive and use the From Drive option.
N.B. this is an embedded item, so the table itself will not realign as the site responds to different device screen sizes, and will not get indexed in search. But when viewing on a mobile device (or a size that makes the table too small to read) Google Sites provides a link, in the top right corner of the drawing, to the full version.
Here is an example html to a table - 2 rows x 2 columns
<table>
<tr>
<th>First Name</th>
<th>Last Name</th>
</tr>
<tr>
<td>James</td>
<td>Adams</td>
</tr>
<td>Janey</td>
<td>Daniels</td>
<tr>
</tr>
</table>
n.b. . <th>
is the table header row
<html>
<head>
<style>
table, th, td {
border: 1px solid black;
}
</style>
</head>
<body>
<table style="width:100%">
<tr>
<th>Firstname</th>
<th>Lastname</th>
</tr>
<tr>
<td>Jill</td>
<td>Smith</td>
</tr>
<tr>
<td>Eve</td>
<td>Jackson</td>
</tr>
</table>
</body>
</html>