Preheat your oven according to the cake box instructions.
Add cupcake liners to your muffin tins.
Chop up your cherries/nuts; set aside.
In a large mixing bowl, add your cake mix, eggs, oil, seltzer water, drained, chopped cherries, and pudding mix. Mix all your ingredients until combined.
Add your mixture to your cupcake papers in the tins. Fill them a little over halfway.
Bake according to the box's instructions for that particular pan. The cooking time should remain almost identical. Mine baked for 18 minutes
I suggest using a toothpick, and checking your cupcakes right at the time the instructions call for.
Add one cherry to the center of each cupcake but gently pressing down. You may need to slightly break the surface. Additionally, you could ice them and then add the cherry.