Pierce peppers with a fork. Combine peppers, vinegar, thyme, and garlic in a glass jar; let stand 2 to 3 days. Strain seasoned vinegar before serving.
Remove stems and center ribs from the Swiss chard, and wash the leaves thoroughly. Combine Swiss chard and water in a large Dutch oven; cover and cook over medium heat for 5 minutes or until tender. Serve with the seasoned vinegar.