I've said it before and I'll say it again salt salt salt, most likely if you are exercising and drinking litres and litres of water you have flushed your body of salt, which makes you dizzy , light headed, hot flushes, cramp, and feel faint.
A lot of people drink far too much fluid if you ask me, what really does your body need 4 litres of water for per day, yes we need to flush toxins but there is also such a thing as putting our kidneys under too much strain flooding it with fluid. Exercising in the first 2 weeks is very difficult, your body has not had time to adjust to burning ketones for fuel and it's another reason you are feeling so bad.
2 cups of bouillon and 2-3 litres of water is fine per day