In case you missed it, I’ve already documented the makeup of clouds when describing how they harvest helium.  The TL;DR version is that helium rises from natural gas in the earth and forms clouds by supporting the water in the atmosphere, so clouds are mostly helium, water, and a little unbound hydrogen and oxygen.  We can work out what effect it would have to eat this.

Helium is an inert gas, meaning it doesn’t react with the human body in any way.  If you inhale it, you get the funny voice thing, which is harmless.  It can’t give you cancer (no matter what the Daily Mail might say).  The only thing helium can do is to deprive you of oxygen if you inhale too much, but that would be your own silly fault.  As far as eating it goes, you’re not really going to see any adverse effects other than gas and skewed readings from your bathroom scales.

Again, eating a little water is not going to do you any harm.  It’s distilled water with no impurities so will probably taste nice too.

The remaining trace gases are unlikely to have any effect on you, with the possible exception of giving you strange-smelling burps.

If you do plan on eating clouds, you are likely to get serious wind so I suggest keeping some indigestion tablets handy.