Wash a 1.5-litre glass bottle thoroughly and dry it completely.
Carefully wash the sloes, pat them dry and discard any that are damaged.
Add the clean, dry sloes to the bottle.
Add the coffee beans and a strip of orange peel (just the outer, coloured zest, no white pith).
Pour in the sweet anise liqueur until it covers the sloes and fills the bottle, then seal it tightly.
Store the bottle in a cool, dark place and shake it gently every day for the first few days, then once a week.
Leave it to infuse for at least 3–4 months (up to 6 months for a more intense flavour).
Strain the liqueur through a fine mesh sieve lined with muslin or a coffee filter into a clean bottle. Discard the sloes and serve the liqueur chilled.