This one really works well to remind you to get up from your desk and go get your water, take a break ….
Just go to google.com and search for “set timer for 45 minutes” or however long you want. A timer will start, and a very noticeable alarm will start playing over your computer speakers.
How long to take off? If your job is mostly in front of a computer, there’s a good suggestion afoot that says to take 5 minutes every hour for 2-3 repetitions, then take 30 minutes away, then repeat as needed. Which lines up with the idea of having something to eat every 2-3 hours, and lines up with the work day at your office pretty well too.