Simple, use nowrap tag.

Example:
[html]<table>
<tr>
<td nowrap>Do not break this very loooooooooooooooooooooooooooooooooooooong sentence!</td>
</tr>
</table>[/html]

Or:
[html]<table>
<tr>
<td nowrap="nowrap">Do not break this very loooooooooooooooooooooooooooooooooooooong sentence!</td>
</tr>
</table>[/html]