Sacrifice a hex tool by aralditing it to the head of the bolt, but that works for one (or two if you use the other end)
A weaker glue may work if the bolts are not too tight, then you can seperate and go for be next bolt
Try the wrong size / mix imperial and metric to see if you can get enough grip
Use a penknife as a screwdriver
Cut into the head to make a screwdriver slot
Drill into the head - but this only separates and leaves the body of the bolt
Use a screw extraction set - reverse drill a tool into the head and then unscrew the bolt using the tool