In the states, you'd go to your local pharmacy/drug store... in the back where they have the cleaners you'll "almost" miss (if you're not careful) a small (think 2" high by 1" wide) bottle of TERRO Ant Killer.
I've found it at Walgreens and CVS. It's about $3-$4 and one bottle is two life-time's supply. You'll put a single
drop (it's thick like syrup) on a penny where you spot the little critters. Two days later you pick up the pennies and wash 'em off.
You're done, and so too are the beasties. We call them sugar ants. I've got a bottle that's 2/3rds full and have used it for over ten years. It works.
Good luck, and happy cruising.