The short answer from a dietitian
Q: Can I make a trip to the Beer Tent after I finish running my race?
A: One beer shouldn’t do too much harm if you have been hydrating properly throughout the race. However, if you are a beginner runner with limited hydration, make sure you are drinking plenty of water if you choose to indulge.
Photo Credit: Josiah Mackenzie from San Francisco, USA [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons