use some kind of spray cleaner to disrupt a large portion of their path so that they cannot follow the scent trail. trace the trail to whatever microscopic hole they are entering from and plug that with tape or something. commonly available traps do not seem to work. we had a big ant problem this year and eventually had to just ask the landlord to send pest control, which is not my preferred solution because who knows what kind of disruption that causes to other lifeforms... it's unkind.