Yes, I’m drinking a combination of water, green tea, camomile tea, and long blacks/Americanos (express and hot water only), to keep hunger at bay. Basically if no calories you’re ok.
Have a read of the sticky post.
Both still and sparkling water is great! A bit of salt now and then can be useful since you could get low on sodium.
Edit to add: unflavored is recommended since adding flavors/sweetener can make you crave food and make it harder to fast.
Only time you wouldnt is if you’re doing a dry fast and the only time I’ve heard of people doing that is for religious reasons and to drop water weight fast for weight check in for wrestling or before a body building show.