sperm strengthening products

Any tried and tested or highly recommended products on the market for strengthening sperm? My friend's husband has been told he has lots of sperm but they are very lazy and weak. they've been battling for 3 years and finally conceived around April last year (naturally) but now they've been for fertility testing and Dr says husband is the one with the "problem". They trying to save up for IVF but until then they still trying to conceive naturally again.