My co-tester Kat Merck (on the now-discontinued Chivalz) and I made so very many slushies with each machine, from dairy to nondairy to coffee slushies to straight-up bottles of wine. Specifically, we tested every version of slush that a machine advertised. If Ninja or GreenPan says a machine can make frappés and milkshakes and frozen juices, we made frappés and milkshakes and frozen juices, tinkering where necessary. I froze orange juice and strawberry juice, slushed a bouquet’s worth of rosé, and made slushies from daiquiri to margarita to whiskey Coke. I slushed tamarind micheladas (an excellent idea) and Twisted Tea (a terrible idea).

Photograph: Kat Merck

I also raced the freezing capabilities of all three machines by pouring a 16-ounce can of delicious Mango Mike’s Harder Lemonade in each, then seeing which machine was fastest. (For the XL, I used a 24-ounce can.) And I made smooth and dense coconut-lime daiquiris with coconut milk, according to Ninja’s recipe, to test how well each machine’s dispenser handled a genuine dense-textured challenge.

The tech is pretty simple, almost ingeniously so: A beefy cylindrical freezing core in the center of the drink chamber continually cools any liquid in contact with it. It’s encircled by a plastic spiral auger attached to a motor. The auger mixes the drink, keeps it slushing instead of freezing solid, and also pushes the resulting slush toward the dispenser nozzle so you can have some. The resolute simplicity of this design allowed Ninja and others to scale down the commercial slushie maker for home consumers thirsty for frozen treats.

The main requirement is that the frozen beverage have more than 4 percent sugar—or between 3 percent and 16 percent alcohol—in order to lower the freezing point of the resulting concoction and make slushing possible. Some slushie machine vendors recommend percentages more like 15 percent sugar, for perfect consistency. But I often balk at this. Coca-Cola and orange juice are each around 11 percent sugar—so that’s very sweet. Some hero of the internet has made a slush calculator for easy reference.

A minimum of 16 ounces of liquid is required for most 88-ounce home machines, for simple reasons: The liquid needs to be in physical contact with the core in order to slush up and also to keep ice from forming on the central cylinder’s surface. The Slushi XL requires a 24-ounce minimum, because it’s bigger.

No and yes. Slushies rely on a helpful property of water: Sugar (or salt) dissolved in water lowers its freezing point below 32 degrees Fahrenheit. Why? Solubles like sugar are chaos agents. Sugar molecules move randomly, refuse to dissolve into ice, and interfere with water’s ability to form hydrogen bonds and turn crystalline. Some water molecules freeze, but sugar water doesn’t. Tada! Slush.

If you try to make a slushie out of sugar-free soda, or sugar-free anything, ice crystals will instead form easily. The stainless steel freezing core will ice over and scrape on the auger, and ice cubes or hunks will gather mass in the slushie machine. The cylinder will start to shake, then the machine will clunk, then eventually you’ll probably break your machine: Low-sugar fail-safes on these devices have not been overly reliable, alas. So don’t try this at home!

This doesn’t mean you’re doomed to massive calories if you want to make a slushie. Not every artificial sweetener lowers the freezing point appropriately, but the one that Ninja recommends for diet slushies is allulose, a rare but naturally occurring sugar that’s 70 percent as sweet as basic sugar but is not metabolized effectively by the human digestive system. This means it’s low in calories and doesn’t cause insulin spikes—but as with a lot of indigestibles, note that side effects can include bloating or GI distress for some.

For easiest use in a slushie, buy liquid allulose. Powdered versions also exist, but to use them, you’ll need to make a simple syrup by heating up the powder in water to help it dissolve, then let it cool. If you just try to drop the allulose powder into your machine with some Diet Coke, it might not dissolve, and you might still get ice formation. Or at least, I definitely still got ice formation when I tried this on the OG Ninja, and had to stop my machine.

Bet you didn’t expect a lesson in milk proteins today! But here’s the deal: Milk proteins start to separate when agitated. Churning milk is, in fact, how butter gets made. Proteins separate out, and you get butter on the one side and buttermilk on the other. Both are delicious, but neither is wanted in a milkshake.

Photograph: Matthew Korfhage

If you try to make a milkshake in a churning slushie machine using just milk, you’ll eventually start to see the effects of these milk proteins separating out from buttermilk—which will manifest first as an undesirable foaminess. To avoid this, Ninja recommends also adding heavy cream or half-and-half to any milkshake recipe. The higher fat content will keep things smoother.

Note it’s easiest to use fruit syrups, rather than just juice, and add vanillin, or it’ll be a bit boring: The heavy fat tends to overwhelm any subtle fruit flavors. Another deep secret of the tasty milkshake? Salt. Add a tiiiinny pinch; it’ll help bring out flavor. A 16-ounce McDonald’s milkshake has 260 milligrams of sodium—about 1/16th of a teaspoon of table salt, or approximately the amount that fits between your index finger and your thumb.

But temper your expectations here. None of the slushie machines we tested made a texture comparable to a classic milkshake. On most machines, which don’t have compressors as powerful as the new-model Ninjas that are now our top picks, the texture is often a little ice-gritty and not as richly textured or integrated as the milkshake you’ll get from your local burger joint, let alone the soft serve from the famously broken ice cream machines at McDonald’s. Slushie machines also can’t handle chunks of frozen fruit, often the best part of a milkshake.

On the newer Ninjas, with their more powerful freezing power, I was able to get the smoothness and freeze I wanted. But because most recipes call for a high-fat mix of 2:1 milk and heavy cream in order ot avoid churning foam and butter, the results still weren’t quite a light milkshake. It was more like a dense, rich, quite tasty soft serve.

Now, do I like being able to make 20-minute soft-serve in my home? From milk and heavy cream and sugar and a dash of vanilla? Heck yes, I do.