The only time I've had it be too sweet is when I let it marinade too long. Also why I prefer coke ad RC over Pepsi or Dr. Pepper, they have a bit less sweetness too them.
You can also try adding soy, worchester, or beer. Be careful with the salts if you use the sauces and watch the amount of beer if you use it, it will make your steak taste just like beer if you use too much.
It's the acid in the soda that does it though. It really helps to tenderize the meat. Make sure it doesn't marinade too long or it will do the same thing as lemon juice and start cooking your meat.
