I flew LHR-ORD today in J - two options, beef or chicken, catered out of DFW. Apparently pax with dietary restrictions were contacted in the morning alerting them to this. Purser said only around 25% of the flights are managing to get catered today. Everyone got a meal, but DFW was scrambling to get anything on board, so we got breakfast for our pre-arrival meal. I didn't bother with lunch as I had enough in the lounge. FAs were trying to make the best of the situation. Alcohol stocks were dangerously low by the end of the flight. They also ran out of clean glassware so swapped to plastic pretty quickly.