Cleaning UV Filter

I noticed some minor smudges on the front of filter. Usually can remove by breathing on it and using cleaning cloth designed for eye glasses.

If this doesn't do it is it OK to use either eye glasses lens cleaner on the cloth or just a spot of water on the cloth?

Water probably won't hurt. I'd be careful of cleaning solutions, however, as your filter likely has anti-reflection coatings on it. I have no idea how delicate these are, so I'm not giving you a caution here, but because I'm ignorant, I'd stay away from cleaners which don't specifically say they are for coated optics. My eyeglass cleaner is made by Zeiss, and specifically indicates it is safe with all coated lenses.

muli-coated filters are quite sensitive. I use one of those lens pens, works every time... but then again, I don't shoot in sand storms either.