Here is the fragment again:
For example, sand-encrusted feet or a cold drink in a sweating bottle.
You correctly identified the fragment as an afterthought phrase. For example, the transition that begins the phrase, is the clue.
To fix this fragment, you could add a subject and verb, like this:
For example, Geraldo
will not tolerate sand-encrusted feet or a cold
drink in a sweating bottle in his new car.
Or you could use Punctuation Rule 7:
Main Clause + , + Afterthought Transition + Ø + Details.
The correction would look like this:
Geraldo will not tolerate anything messy in his
new car, such as
sand-encrusted feet or a cold drink in a sweating bottle.
Notice that for example has become such as. It is best to save for example to introduce a main clause. If the afterthought comes at the end of a main clause, change the transition to such as, like, or including.
Enjoy the sound of those bells!