This is a yummy, warm drink, recipe you make in your crock pot. I found the recipe in "101 more things to do with a slow cooker."
You can use different flavors for the gelatin. I think the fruity flavors are the best: strawberry, raspberry, peach, cherry etc.
I don't recall having any problems with the gelatin dissolving, but if you are concerned you could microwave a couple of cups of juice to boiling and add the gelatin to the hot juice and then add the juce to the crockpot.