In a stockpot over medium-high heat, bring vinegar, water, sugar, salt, peppercorns, and bay leaf to a boil, stirring until sugar dissolves. Add vegetables and reduce heat to a simmer. Cook until vegetables are tender, about 10 to 20 minutes. Remove from heat and let cool completely. Transfer to an airtight container with liquid and refrigerate until serving. Better to wait 3 days before serving (keeps about 2 weeks). Drain before serving. Cool in refrigerator.