Simple:
* The stock market experienced fluctuations throughout the day.
* There was a fluctuation in the temperature throughout the night.
More complex:
* The fluctuations in the economy made it difficult to plan for the future.
* The fluctuation of the tides is a natural phenomenon.
* Despite the fluctuation in sales, the company remained profitable.
* Her mood fluctuated wildly, from joy to anger in an instant.
Figurative:
* The artist's style fluctuated throughout their career, from realism to abstract expressionism.
* His attention fluctuated between the book and the buzzing fly on the windowsill.