Put the yogurt with the chilli, mint, coriander, dill and sugar in a bowl. Season and mix well. Pour into a fine sieve set over a bowl. Cover and chill for 3 hours, or overnight if you have time.
Discard the liquid in the bowl. Scrape the mixture in the sieve into a covered portable container (it should be the consistency of cream cheese). Drizzle with olive oil and season with pepper. Pack some breadsticks or crudités to serve with the dip.