Cola slug-trap tips:
Using cola to trap slugs and keep them from eating your plants will only work if you set the trap out properly.
Consider burying the bowl in autumnal leaves, or try making a secure covering which surrounds the can or bowl to disguise the sweet liquid.
Position the trap in a lowered ditch to keep it level with the grass for a more effective repellent.
Choose a bowl which is as close to ground level as possible to ensure the slugs are able to slither into the pool of cola.
source: express.co.uk