Thermal Lenses are a must. Most goggle brands can be upgraded to thermal lenses. Unfortunately most rentals are NOT thermals, and fogging is always bad.
There are sprays you can use that will help keep fog down, but they have to be used properly to work. The concept to follow, if you use these sprays or other similar methods, is that you need to leave a macroscopic layer of dried soap residue on the inside of the lense. This works as the thermal layer and inhibits the condensation (fog). So this means when you use the spray, you only lightly dry with a towel or tissue, leave it damp inside but not sopping, and then air dry it. You can help speed the airdrying by waving the goggles around (it's not instant, so wave it for a full minute or two!)
You can use NON-Ammonia window cleaner or just soapy water, or Fog-X towels, or RainX is okay but not as effective, or even people have taken potato cubes and rubbed it on. Once dry, if it's not crystal clear, you very very lightly buff off the residue. Don't overbuff cuz You WANT residue, but you only want a thin layer that doesn't block your vision.
Nothing is worse than not being able to see on the fields, so it's definitely worth the time and effort to do this right, or get some thermals!
There is a trick to wiping the insides of your goggles with a paper towel while NOT removing your goggles. Carry folded squares of paper towel in your pocket, kneel down behind GOOD cover, do not present a target when you do this, tuck yourself as tight as you can behind the cover and with one hand pull your goggles out AWAY from your face (NOT UP, NOT DOWN, AWAY so that your face is still protected.) just enough to slide your other hand with the square of paper towel, up past your nose and into the mask. Couple of swipes, then pull out. If your mask doesn't have ear flaps do NOT do this. Do NOT do this if you're in a heavy firefight, you risk injury. Do NOT do this trick on a speedball field because the game is too fluid and fast for you to be sure of the safety.
It's vital that you NEVER remove the goggles on field even if you can't see a thing.