Yes, you can absolutely take your own water bottle on the Eurostar in 2026, and unlike air travel, there are no restrictions on liquids. You can bring a full 1.5-liter bottle of water, a thermos of hot coffee, or even a bottle of wine or cider through the security check at London St. Pancras, Paris Gare du Nord, or Brussels Midi. The security process for Eurostar is much more "relaxed" than an airport; while your bags go through an X-ray machine and you walk through a metal detector, you do not have to remove liquids from your bag or follow the "100ml rule." This is a significant advantage for 2026 travelers looking to save money, as the food and drinks at the onboard "Café Métropole" can be quite pricey. A "pro-tip" is to bring a reusable insulated bottle; most Eurostar stations now have free water refill stations, allowing you to stay hydrated throughout your journey under the English Channel without contributing to single-use plastic waste.