One of our favorite uses of whey is making probiotic lemonade. I canned some strawberry lemonade concentrate this past summer. Here is the link to the recipe I used. All I add is whey and some sugar. The bacteria need to feed on sugar. I still want it sweet so you need to add extra. The extra sugar is ate up by the healthy bacteria!
You need a gallon glass container and filtered water too! I put mine in a gallon drink dispenser. That way when it is finished I just put it right into the fridge and dispense it from there.
Put the concentrate in your container. Add 1 cup of sugar and 1 cup of whey. Add enough filtered warm water to dissolve sugar. Stir until the sugar is dissolved. Then add enough filtered water to fill the container. Leave about a 1 inch head space. Cover and let sit for 2 to 3 days. After 2 days check it. It should be super fizzy and Carbon dioxide bubbles should be seen rising up and down in the container. If it is not real fizzy let it go one more day. You don't want it to go too long because it will start to turn to alcohol. Which is fine if you want that, but not good for kids! When it is ready put it in the fridge. This slows down the fermentation process. It will continue to ferment over time so it is best used with in a week. Ours never lasts that long!
The great thing about this lemonade is it is full of probiotics and is great for your gut! I served this recently at my sons birthday party and my dad loved it!