The shelves at Target and Ralphs were wiped out - just bare shelves where normally there would be toilet paper, paper towels, water, and disinfecting wipes. I didn't even see spaces where hand sanitizer would normally go. Costco had two epic lines - one that would give you an opportunity to purchase water and paper goods, and one that would give you access to the rest of the store only. I went to 99 Ranch for rice, and found only brown rice!
Fortunately, we keep emergency supplies on hand, so we have enough water, food, and paper goods to last for a few weeks. I did pick up some extra canned goods and snacks, so we don't have to leave the house as often if some kind of quarantine is put into effect.
In the meantime, if you're concerned about not being able to buy bottled water, consider using a pitcher with a filter or a faucet filter (they're in stock at Target and Amazon).
And if you can, please consider donating to a food bank. This Kitchn article explains how difficult times like this can be for those who can't afford to stock up.