Essentially, so long as you've got a tasty liquid well balanced in the sweet / sharp stakes, you're quids in. The sweetness will fade slightly as the liquid freezes so it's best to be ever-so-slightly over-sweet than under.
I use an ice cream maker but I'm pretty sure you can make without, using some Tupperware and an hourly stir. These are the three I've made so far, you may notice a recurring theme...hic....
Take a 500ml bottle of cider, add 1-2 tbsp of caster sugar and stir to dissolve. Add the juice of one lemon, and taste; it should be tangy and sweet, and - obviously - cidery. Churn until it starts to look like sorbet, then transfer to a tub and pop in the freezer. After an hour, give a good stir, and put back for at least another 4 hours.
Blackberry & Cassis
Put 8 handfuls of clean blackberries into a pan with 200ml water and 2tbsp of cater sugar, and simmer gently for 5 or 6 minutes. Push the berries through a sieve, and discard the pulpy pips. Add the juice of a lemon to the liquid and a good slug of cassis and taste; again, tangy, sweet, fruity - you may need more sugar depending on your berries. Leave to cool, churn, and freeze as above.
Pink Grapefruit & Gin
Heat 150ml water and the juice of 6 pink grapefruit with 2-3tbsp caster sugar until boiling point is reached and the sugar has dissolved. Taste for sweetness - adjust if necessary - and leave to cool. Once cool, add 60ml gin, taste, and churn as above.
Serving three boozy sorbets together allows you to make different 'cocktails' with each spoonful - what fun! All boozy sorbet suggestions welcome....I think margarita is next on the list.