I use this method for my tomatos but it works equally well on other garden plants as well.
Step 1: Increase Your Sunshine and Get Rid of Pests
The shine of the foil will also discourage birds from destroying your plants and give an inceased amount of sunshine on overcast days.
Step 2: Sweeten Your Tomatos
I used a lot of baking soda in his picture so it would show up but about 1/4 cup per plant is plenty.
Note: I have not used this on other plants and have no idea what effect it would have other than with tomatos.
Step 3: Reap the Early Harvest
It is too early for me to pick my tomatos yet so I had to use red ones for the picture instead of green.
Step 4: UPDATE -
I wear a small glove and this tomato is a handful, about 10 inches around.
Just a little bigger than a baseball.