This evening I finally got around to marking up some of my water bottles with one-third and half marks. Since I frequently mix up two or three hours worth of sports drink stuff in them (typically from Infinit Nutrition) I like to drink half or one third of the bottle per hour. I’d previously guessed at what 1/3 and 1/2 of the volume would be, but apparently I was a bit off. The dent in the bottle must have thrown me a bit.
By the time these markings wear off I’ll likely have these levels memorized and won’t need to redo them.
(Note that this bottle contains enough mix to meet my caloric needs for three hours of riding. Despite being filled to just below the Breakaway Bicycles & Fitness logo it’ll all dissolve pretty readily in one bottle of water.)