You really need 6 10 oz. lemonades minimum to keep your energy up (I do my regular gym workout every day of the MC--you can't say that about water fasting!). If it's the cayenne, my wonderful naturopath has me take it in capsules -- 3 caps a day with lemonade. I prefer it that way, though purists insist the only way is to chug it in the juice.
If lemonade isn't for you, consider doing a juice fast. It's more work, but very supportive, very cleansing and tasty!