1. In two quart-size glass jars, arrange beans upright and place 2 sprigs thyme in each jar. In a small saucepan, bring vinegar, sugar, garlic, fennel seeds, coriander seeds, mustard seeds, peppercorns, and 1 cup water to a boil over medium-high. Reduce heat and simmer 10 minutes. Let cool to room temperature.

2. Pour cooled brine over beans, leaving a 1/2-inch space at top of each jar; seal and refrigerate at least 3 days before serving.