Sponsored Posts are what Google calls advertorials and considered to be a link scheme[1] which means they're against their webmaster guidelines[2].
However, they're acceptable if they do not carry any link equity (aka. use the no follow tag) on the link.
[1] https://support.google.com/webmasters/answer/66356
[2] https://support.google.com/webmasters/answer/35769?hl=en