The Houston-native is donating 20,000 cases of water to victims affected by the catastrophic floods. The music honcho -- along with his partners Chris Kotz and Vivian K. Gomez -- own a natural water company called Honey Water.

Jas sprung into action after TMZ reported a Best Buy store and other retailers were caught selling packs of water at obscene prices ... as high as $42.

Best Buy has since apologized, but Jas is still furious ... telling TMZ, "It's f****** ridiculous that people instead of coming together to help one another are trying to profit from such a heartbreaking disaster. That doesn't sit well with me and I won't allow that in my city."

IF you're thinking Jas' gesture is a mere marketing ploy, don't.

You can't buy Honey Water in the U.S. ... only in Canada.