Help! How can I get rid of these ants?

My roommate and I keep the apartment spotlessly clean and never leave dishes in the sink, and yet we have a horrible ant problem. This all started at the beginning of the summer and has gotten worse over the months. At first they were just in the kitchen. Then we started seeing them in the bathrooms and now they’re in my closet! I have absolutely no source of food in the closet, so I don’t understand why they’re in there. We’ve already had pest control come spray the place multiple times but that only seems to work temporarily (for a day or two).

What else can we possibly do to make these pesky ants go away? Are you aware of any DIY methods that actually work?

Thanks in advance!