Small coolers strapped to front and rear racks. Divide a case between two 9-quart hard coolers, like Igloo’s Island Breeze models. Use net bungees to secure them to your bike. Pros: Good insulation. Cons: hard to access if bungee cords go over lid.
Small coolers in grocery panniers. Many small coolers fit perfectly into grocery panniers, which are open at the top. Make sure to drink equally from each side to avoid balance issues. Pros: No bungees necessary, easily accessible – even on the go. Cons: Tops of coolers may pop open over rough terrain.