maybe like 1 hour a day for 5 days?
You'll only lose water, so there will be an initial drastic loss, but once you drink water, your body will absorb it again and the weight will come back.  If you don't replenish the fluids, you risk damaging your liver and kidneys along with a constant thirst.  It's not a healthy or lasting diet alternative.
Here's a tip.  Go to France on an exchange program.  You will learn more French in one month than in a year of study.  Check around.  There are some summer programs that are not that expensive.