Siphoning into jerry cans is the usual approach. You can get cheap (and inexpensive) pumps that are used with an electric drill. The problem is that the hoses are small in diameter and the pumps are slow.
Depends on why he is draining the tank, if the fuel is contaminated...Remove your fuel return line. With small nipple and extra fuel hose added to nipple, direct the fuel return to your jerry can. Start motor and shut off when can is full or fuel is down to the pick up level. If you let the fuel pump below the pick up level, the motor will shut off all by itself!!