Thanks so much!! Yes you can definitely substitute the sugar, corn syrup and lemon. To be honest, strawberries are already pretty sweet, you could probably add a little bit of honey and thats it! Just remember that if you want to can the recipe then you MUST follow it exactly, you can't make any substitutions otherwise it is not safe to can!! But feel free to make substitutions in the recipe if you're not going to can it, it should last in the fridge for a while anyway :)