TOASTER Defrost until soft enough to cut and toast until golden brown.
OVEN Reheat for 6-8 minutes in a pre-heated oven from frozen at 180 degrees (160 if fan assisted).
MICROWAVE Defrost until soft enough. Sprinkle the bagel with water and microwave it for 30 seconds.
ELECTRIC HOT PLATE Cut it half, place in frying pan, cover to retain heat & moisture and cook on a low/medium heat until warm all the way through.