Here is a trick next time you are at a café having a coffee. Typically, you'll have your coffee delivered to the table with two sugar satchels. You only need one of these satchels. Pocket the other one.
Next, go home and save the next plastic 2 litre milk container that you are putting out in the recycling bin. Better still, save two 2 litre containers.
Cut the containers at the half-way mark.
Fill with water to 20 millimetre mark.
Stir in sugar until it dissolves.
I've had a record of fourteen cockroaches on one night. It is a great chemical free way of pest control. You will catch some non-target beasties - ants and beetles - yet that's okay as you want to rid of cockroaches.
In hot weather you'll find that the water solution dries out. Practically, the water needs toping up every second day. You'll want to replace the container entirely every fortnight.
I've saved you from an 'after' photo.