Answer:
180 W
Explanation:
The work done by the man against gravity is equal to its gain in gravitational potential energy:

where
(mg) = 720 N is the weight of the man
is the change in height
Substituting,

The power he must deliver is given by

where
W = 3600 J
t = 20 s is the time taken
Substituting,

Weight = (mass) x (gravity)
If you plan to sell these things on Earth, then the acceleration of gravity in the neighborhood of your drive-throughs will be 9.81 m/s².
Weight of each sandwich = (0.1 kg) x (9.81 m/s²).
Weight of each sandwich = 0.981 Newton.
This is only 1.9% less than 1 even Newton.
You should start by setting up one restaurant in New York, one in Chicago, one in LA, and maybe one in Miami or Tulsa. Sell it with a different name in each place, and see which name sells best.
You might want to try calling it
-- Isaac's burger
-- Gravity grub
-- Prism Patty
-- Mass 'o Meat
-- Unit-wich
and see if anything catches on.
I think I'd simply call it a "Newton Unit".
Material that is not attracted to metal