Mostly everyone remembers hearing about astronaut food when they were a kid. The freeze-dried packages of ice cream and other foods taken aboard space flights so that space crews would have something to eat.
The official Nasa drink back then, was reportedly, Tang. For those of you unfamiliar with Tang, it is a powdered orange-flavored drink made mostly of sugar, but also containing 100% of the RDA of vitamin C. When I was a kid, my mother would take a container of Tang with us on vacations, presumably because it was easy to take along (probably why the astronauts took it to space too). Oddly enough you can still buy Tang, but as far as I know, it is no longer taken into space.
Astronaut food (other than Tang) is freeze-dried, which removes most of the water, but basically leaves the rest of the food intact. This makes the food very compact and light weight.
In fact, astronaut food has become something of a novelty item and you can buy it from several sources, such as Amazon.com, for example.
Does it tastes good? Well...that is a matter of individual taste.
Most commonly, you'll find the desserts. I'm fairly certain that astronauts would've needed something more than sweet foods, but it could be that the meats and other foods aren't that tasty and that is probably why you don't often find them for sale.
Personally, I've tried astronaut fries, the ice cream, and of course, Tang.
Here is a great video that shows someone fixing an astronaut meal of beef stew, corn, and pudding.
So do astronauts still eat this stuff?
When you watch TV or movies, you usually see one extreme or the other. Astronauts eating only freeze-dried foods in foil packets or delicious looking plates of fresh vegetables and other foods (like on Star Trek - those people had the healthiest looking foods, much better than what I get to eat here on Earth). It must be great to have a replicator!
Currently, astronauts eat more typical to what you find here on Earth and I doubt you still find packets of freeze-dried ice cream on board the spaceships. However, in the beginning of space travel, astronauts really did eat the freeze-dried foods, and of course they also drank their Tang.
If you'd like to try some astronaut food for yourself, check out the links below: