Do any drinks violate a fast?
No. But, if you are drinking a ton of something that has a lot of caffeine, calories, etc. and it means you can't quite feel the effects of a fast, then it isn't quite part of the "spirit" of fasting.
How much can I eat when I fast?
The Church law says you can have one meal and two small snacks. But, remember the point to all of this isn't to get caught up in the details, but to allow our bodies to reflect the inner mortification and prayer our souls are caught up into. Without the spiritual effect, the bodily doesn't matter.
I heard you have to abstain from meat every Friday, not just those in Lent, is this true?
No. We are not required to fast every Friday. But, it is still highly recommended that we do some penitential act on every Friday (which could be abstaining from meat). The only days that we (in the US) are required to fast are Ash Wed and Good Friday.