The reason to stockpile food before the coronavirus is so you don’t have to go to the store and buy groceries. This reason doesn’t apply to water and I don’t think there’s any chance the utilities are going to shut down. Even if everyone gets infected, the death rate is low enough the there will still be people keeping stuff running.

Stockpiling some water makes more sense in California where the water is piped in from far away and we are at risk of big earthquakes that can break those pipes.

In an apartment, your best bet for adding water storage is probably stackable 7 gallon jugs like this: https://www.rei.com/product/618168/reliance-aqua-tainer-7-ga...

A gallon per day per person is enough.

If you have land and want to store more, you could get 55 gallon water barrels.