Every Honda and Toyota I've ever owned has needed periodic topping off of the refrigerant.
If you have a sight glass on or near the high side valve, it's easy:
Use straight R-134a - NO OILS, NO SEALS, NO DYES, NO ADDITIVES.
If in doubt, ask an employee of the store.
If they don't know, go somewhere else.
The contents should read: "1,1,1,2-tetrafluoroethane"
The last few cans I bought from Walmart were supertech brand for $4.88.
Get a cheap ($12 or so), low-side fill hose.
Follow hose directions and add R-134a to the low side.
Watch site glass.
Terminate addition of R-134a when the bubbles in the sight glass go away.
If you don't have a site glass, you need to do something like this:
Just DON'T USE THE PRODUCT HE'S USING.
Adding R-134a that contains oil or other additives (mostly the oil, though) to your A/C system could damage the compressor.
Adding straight R-134a is perfectly fine.