Batch #1 - Applejack via freeze distillation
I should start out by saying that home distillation of alcohol is illegal in many countries, unless you plan on using it for fuel. Freeze distillation, also known as fractional freezing, has long been used as a way to increase alcohol content of beverages like ice beer (e.g. Icehouse) and making applejack out of hard apple cider. You can't achieve the same alcohol concentration that you can with evaporative distillation, but the freezing method is cheaper and easier. Freeze distillation removes the water from the alcohols (ethanol, methanol, and fusel alcohols) instead of evaporating and condensing out the desired ethanol from everything else, as in conventional distillation. Methanol and fusel alcohols are generally considered undesirable (and hangover-causing) but they are present in undistilled beer and wine, and contribute to the flavor profile of ales and ciders. But at least with freeze distillation you can't accidentally end up condensing high concentrations of fusel alcohols by evaporating at the wrong temperature. I'm intrigued by some of the homemade evaporation stills I've seen, but I'm still intimidated by the need to keep track of the heads and tails of the process.
So, for this first batch, I added 1/2 cup of sugar every month or so until fermentation no longer re-started after adding sugar. In other words, until it was so alcoholic, yeast could no longer survive. This tolerance depends on the strain of yeast, but ranges from 5% for some beer and baking yeasts, to 23% for some "turbo yeast" strains. I forget what type of yeast I pitched--probably wine or champagne yeast, so I'd guess this batch maxed out at around 12-15% abv. When winter came around I put this batch in a 5-gal on the back porch. Repetitive freeze-thaw cycles are supposed to help with separating water from alcohol. I don't think it actually ever got cold enough to freeze though. Luckily, our freezer was able to get it cold enough, so this spring, I froze it in batches, and let the concentrated applejack strain out, as shown in this video:
And so, one gallon of hard apple cider became one half gallon of applejack. I'd estimate a final alcohol content of 20-30% for the applejack. Although I tried lighting it on fire, it didn't burn, but I did accidentally spill some of the fuel in my mouth, and it does taste really good! I even made a digestif of sorts, by soaking a "cinnamon" stick and cloves in a pint of the applejack. It tastes really good too!
Batch #2 - Sparkling Cider
For the other batch, I wanted to emulate ciders like Strongbow or Woodchuck. After the initial cup of sugar, I didn't add any more until we bottled it. We added priming sugar like you would for beer, aiming for 3 volumes of CO2. The verdict: it is good, but needs some aging to mellow out the flavor.
On a side note, I am super-intrigued by this inexpensive force carbonation method: capturing CO2 from fermentation in a mylar balloon and then force carbonating a mini-keg using a homemade PVC pump!