Melt butter, sugar and vanilla together. (I do it in the microwave.)

Peel apples and slice, lengthways; then place slices in each crescent roll. Roll up from the large end of the crescent roll, using one-and-a-half apples for each can of crescent rolls.

Place in 9 x 13 dish. Pour melted butter mixture over apple/crescent rolls and sprinkle cinnamon on top.

Pour the can of Mountain Dew over dumplings.

Cook at 350° for 40-50 minutes, till golden brown. (We like the crust a little crispier, so I turn the heat up to 375°--or leave it in the oven longer.)