Incorrect spelling, explanation: an apostrophe before s is used only with nouns: to express possessiveness or to shorten verb is or has). Get is a verb so it can’t be used in these contexts. Gets however is a third person singular from the verb get, as we add s to verbs in such cases. Therefore gets is the correct form here, and get’s is incorrect.

Correct spelling, explanation: this form is correct since the third person singular form from get is gets (we add s to the verb). S after an apostrophe is used either for possessiveness or to abbreviate the verb be (is) or have (has) after a noun. Get is a verb so these two options do not apply to it.

Definition of gets:
verb, third person singular of get; to come into possession of something; to become
Jenny is a great student; she always gets straight A’s.
My boyfriend doesn’t wear socks and he never gets cold. Unbelievable!