Tighten the mask
You can adjust the ear loops or ties so the mask fits more snug against your face. Air should not be escaping through the top of the mask if it is fit properly.
Mold your mask
A lot of masks have a bendable metal strip on the top portion that you can mold around your nose. You can use twist ties or pipe cleaners in a homemade mask for the same effect.
Adjust the position of your glasses and your mask
You can try pulling the mask up and having your glasses sit on top of it to hold it in place better, depending on the fit of your glasses on the bridge of your nose.
Put a tissue inside the top of the mask
You can fold a piece of tissue and put it between the top of your mask and your face so that it sits over the bridge of your nose. The tissue will then absorb the moisture from your breath instead of hitting your glasses lenses.
Tape your mask
You can use medical or athletic adhesive to tape the mask on the bridge of your nose and across your cheeks. You want to avoid duct tape and make sure you test a strip of your skin before applying to make sure there are no allergic reactions.
Wash your glasses in soap and water
You can wash your glasses with dish soap and let them dry before putting them on. The surfactant in soap leaves behind a film that helps prevent fogging.
Purchase a commercial anti-fog wipe or spray
These can work really well but are difficult to find or expensive to purchase currently. You need to read the instructions and make sure that they can be used on glasses with anti-glare coatings before applying to your lenses so you do not damage your lens coatings.