Is there an SDK for the Rest API?

https://<instance address>/rest/v11/help

Also check https://support.sugarcrm.com/ and search REST API, you will find some examples

Check the Sugar Developer guide: https://support.sugarcrm.com/Documentation/Sugar_Developer/Sugar_Developer_Guide_10.1/Integration/Web_Services/REST_API/

SOAP is deprecated and not recommended.

Lesley Anderson the SOAP API has been deprecated for about 10 years, it should not be used. There are several SDK libraries available it would depend upon which language you are programming in. Here are a couple of links to libraries 

• https://github.com/sugarcrm/rest-php-client/
• https://github.com/spinegar/sugarcrm7-api-wrapper-class

Official documentation - https://support.sugarcrm.com/Documentation/Sugar_Developer/Sugar_Developer_Guide_10.0/Integration/Web_Services/REST_API/

Examples: https://support.sugarcrm.com/Documentation/Sugar_Developer/Sugar_Developer_Guide_10.0/Cookbook/Web_Services

Thanks, all for the links.

I am still a fan of these even though they are a bit old (good examples):

https://sugarclub.sugarcrm.com/dev-club/b/dev-blog/posts/sugarcrm-cookbook---the-school-of-rest---part-1

https://sugarclub.sugarcrm.com/dev-club/b/dev-blog/posts/sugarcrm-cookbook---the-school-of-rest---part-2

https://sugarclub.sugarcrm.com/dev-club/b/dev-blog/posts/sugarcrm-cookbook---the-school-of-rest---part-3

For SDK - there is https://github.com/sugarcrm/rest-php-client if you're looking for a ready-made wrapper library.

Also, we built an add-on to call/try SugarCRM REST APIs from the browser, using a Swagger API Interface - in case you're interested.