Not per se, but...
It kind of depends on what you're eating and how easy it is to eat your food somewhere else, as well as how uncomfortable Ramadan is at that place and time.
And obviously, try to be discreet about it and not draw your coworker's attention or distract him with the smell or taste.
To elaborate: snacks are pretty much always fine to eat at your desk (that includes fruits, chips, etc... heck, they probably wouldn't even find chips appetizing at that point -- they'd want water and a good meal), as are meals that were prepared earlier in the day (since they're probably cooler and won't have as strong of a smell). But it's a bit distasteful (no pun intended) to eat newly-prepared food that has a highly appetizing smell right beside your coworker's desk if you can reasonably avoid it without much trouble.
For instance, if you have a lounge where people often eat lunch, your coworker would probably appreciate it if you had your hot pizza delivered there instead of within 3 feet of him.
Furthermore, the setting kind of matters too. If it's a hot day, your coworker would not appreciate it if you kept reminding him of water. But if your office is air-conditioned then it's unlikely they would be thirsty at all, so at that point your coworker is almost surely not even going to think about the fact that you have a cup of water/tea or a bag of chips or cookies sitting next to you, unless you make super loud slurping/crunching sounds or something.
People understand, but they're humans too.
The mere fact that you're eating/drinking nearby isn't offensive in any way whatsoever (unless you're in a culture where fasting is the norm, which you're not). However, if you do it in a manner or setting that ends up making this distracting for him and it's clear to everyone that you have a reasonable, alternative lunch setting available to you that could be less distracting with little inconvenience to you, then it would probably bother your coworker.