I was putzing about with our food storage today and came across the Honeyville #10 cans Mr. WPW laid in. I decided to be adventurous and grabbed a can of the most interesting item, the chocolate milk alternative. I expected to hate it, to be honest. I thought it'd be like Yoohoo at best. Happily, I quite liked it. It's clearly not "real" milk, but it didn't have any nasty aftertaste and was quite rich. It also dissolved easily and completely in the water, rather than separating as I expected (and many other powdered drinks do, too). Two thumbs up.
I think I'm going to grab a can or two of the off-the-shelf cans and try them over the next few months. I'll let ya'll know how they turn out.
ETA: After having it sit in the fridge for a short time I do find that you need to stir it well again as it gets a bit separated/clumpy, but that's easily done.