Are you allowed to eat during class? IF so, have a little snack like fruit and peanuts (not too little of a serving) usually 30-45 min before your workout. Personally I cant workout with a semi full stomach (thats me).
Nothings wrong with sipping on a PWO shake, but if youre using it for PWO, shoudnt it be used for a PWO (POST Work Out). Best bet is go for surge!!!
Whats goal? Bulk or Cut?