You need an ETA for Saint Kitts and Nevis if you have an Israeli passport
Visa options for Saint Kitts and Nevis
Electronic travel authorization
Travellers need a travel authorization to visit Saint Kitts and Nevis for Business or Tourism. Visa-exempt visitors entering Saint Kitts and Nevis must obtain an Electronic Travel Authorization (eTA). Travellers can submit the eTA application online. Once the application is approved, travellers receive their eTA confirmation electronically. If travellers receive a new passport, they must apply for a new eTA.
This is not offered by sherpa°.
Apply on the government site.