Patrick Huseneau's Solution

Let's name the jugs:

A = 3 L
B = 5 L
C = 8 L

We begin with 8 L in C while A and B are each empty:

A = 0
B = 0
C = 8

To solve the puzzle, proceed as follows:

1. Pour from C into A.
   Status: A = 3, B = 0, C = 5
2. Pour from A into B.
   Status: A = 0, B = 3, C = 5
3. Pour from C into A,
   so A = 3, B = 3, C = 2. Already half of the job is done and there is no waste of the precious liquid so far.
4. Pour from A into B and use 1 L for something else.
   Status: A = 0, B = 5, C = 2
5. Pour from B into A.
   Status: A = 3, B = 2, C = 2
6. Pour from B into C or C into B to have 4 L.
   Status: A = 3, B = 4, C = 0

That’s it!