In reponse to various questions that have arisen before and during Pesach, Matzav.com wishes to inform readers that all unflavored bottled water, seltzer and sparkling water without any additives are kosher l’Pesach, even without any kashrus supervision.
This has been confirmed by Matzav.com with the Orthodox Union and other kashrus agencies.
The above applies only to unflavored varieties, as mentioned.

In addition, whole eggs in their shell may be used without special Pesach certification.
{Matzav.com}