Thanks a million for your reply. Still in two minds, my class is two hours with no break and it's fairly intense, so I might just show up and explain to my instructor what I'm doing and tell him I might need to take a break or leave early. A smoothie wouldn't be ok as I don't want my digestion to kick in, I'm just doing juices, water and broth - but I could make myself a big fruit juice and bring it along in a bottle in case I start to fade! Thanks again :)