The cap on the Spartan Mosquito Eradicator has small holes that, unfortunately, mosquitoes do not use. As a result the mosquitoes are not killed by the fluid inside. Actually, even if the mosquitoes did squeeze inside the fluid wouldn't kill them because mosquitoes are not stupid enough to drink the sugar/salt water. And even if there was an occasional stupid mosquito that did, it wouldn't likely kill it ... mosquitoes deal with salt all the time in the form of blood. They just excrete the salts in their urine after they bite us.
Anyway, the Spartan Mosquito Eradicator is designed to *seem* like it might be killing mosquitoes. Through confirmation bias and marketing there are now tens of thousands of people who are fully convinced the devices work. In reality the product doesn't work and, I suspect, the owners fully know that. They are getting rich.
Some governmental agencies are looking into revoking the ability of the company to sell the product. So if you swear by it, you should stock up fast.
My review in case anyone is interested in the details:
https://colinpurrington.com/2019/08/spartan-mosquito-eradicator/.