It’s just a mix of water, brown sugar and yeast:
1. Cut a plastic bottle in half, keep both parts. Can be CocaCola/Pepsi. No matter lah!
2. Take the lower portion of the bottle. Dissolve the brown sugar in hot water. Let it cool down to ~70 degF.
3. Add the yeast. Carbon dioxide will form (This will attract the mosquitos)
4. Cover the bottle with a dark wrap and place the top portion upside down like a funnel. Place it in a corner in your house.
5. In 2 weeks you will be surprised by the number of mosquitos killed. Check this this link and this other link.