In a large skillet, add the onions, butter, chicken broth, and sugar.
Bring the mixture to a boil then reduce heat to simmer.
Stirring occasionally, cook over medium-low heat until the onions start to soften and the liquid has evaporated. This should take between 15 to 20 minutes.
Add the water and cook until the onions are glazed. That’s around an extra 10 minutes.
Remove from heat.
Stir in vinegar and thyme.
Top with thyme sprigs and serve.