Training before breakfast?

[CrazyEnglishTriathlete]

Up to about two hours is fine.  I often used to go out for 60 - 90 minutes on just a bottle of water.  I prefer to do my running training first thing before eating and again I can just about do a half-marathon (as long as its not too hot) before breakfast, which is about an hour-an-three-quarters.  I do tend to have two breakfasts though - one when I get in, and another at 10.30

[TigaSefi]

Had a bit of toast, then wattbike for 10 mins and cereal afterwards. Felt fine. Will see how I do when I push to 20/30 mins mark in the mornings. I know I'll need a LOT more water.

[Ningishzidda]

As CET says, up to two hours is fine on a cup of water.

A rough-and-ready quick calc for H2O is 1 cm^3 per 4 kCals used. At a nominal 12 kCals/min, 3cm^3 per minute will keep you hydrated, so half an hour is 90 cm^3. Your body won’t miss that much.