Little antifreeze in hot water tank a problem?

I did this once too. Felt like a fool. You might want to get a tank rinser. Don't know if that's it's real name, bit it's just a tube with a little bend at one end and a standard female garden hose connector on the other. And happily it's very inexpensive. You insert it after removing the anode rod and flush out the tank. Even if you don't need to flush antifreeze it's useful to flush out crud from the tank. You'd be surprised at the mineral deposits and other stuff that collects in there.