Ideas about what to do with juice concentrate?

Apple cider doughnuts! Boil apple juice concentrate with an equal amount of butter, and dip homemade cake doughnuts on both sides, then sprinkle with cinnamon sugar. They are excellent. I use King Arthur Flour's recipe for "Baked Doughnuts, Three Ways".

Get yourself some unflavored gelatine and make jigglers, or even jello. To make a small batch of juice jiggles- soften 2 envelopes of gelatine in 1/2 cup of cold juice, in a large bowl. Let that sit for a minute, or while you bring another 1 1/2 cups juice to a boil. Add the hot juice to the bowl of cold juice, and stir until it is all dissolved and mixed well. Pour that into a pan sprayed with nonstick spray, and chill until it sets up. Cut into whatever shapes you like. You can also cook tapioca pearls in juice, instead of milk. When mine were young, that was a favorite dessert. You can mix in other fruit, marshmallows, or whatever to make it special. Finally, you can mix up the juice as if to make jello, but use that to make a jello poke cake. Use a plain yellow or white cake mix- or make your own from scratch, in a 9x12 baking pan. After it cools, poke it with a fork in a regular pattern. Pour the unset jello liquid over the top of the cake, and chill it for a few hours. Serve that as it is, or topped with whipped cream and fruit to match or compliment.

You might consider going into sorbets or sherbets- I haven't done so, but the booklet that came with my (crummy) churn has a lemon ice recipe containing 1- 12oz. can lemonade concentrate, 3c. water and 1 1/2c. sugar, and a sherbet that uses 1 cup lemonade concentrate,3c. milk,1/2c. sugar, 2Tb. lemon zest and 1 egg white. If you enjoy searching recipes there are probably a ton out there, and churnless versions, but I haven't researched them myself.

If you like these products, use them in fruit salads, in baking instead of some of the liquid (replaces water or wine, not milk or dairy), homemade frozen popsicles.
But/and they are high in sugar, so eat in moderation.
Also the ones in the freezer last a long time...maybe a year...so no rush to use up.