Best option for topping up?

If you are supposed to rack into secondary, then every 30-60 days until no longer dropping sediment before bottling, what is the best way to top up?

I know ideally I could just make extra traditional to top up with, but in the event that isn't an option, what is the best?

I don't have marbles handy.

Honey water? Fruit juice? Plain water?

I just topped some up with filtered water, but it dawned on me that it may cause the final product to be watered down?

Any experiences?

You should not rack so often, rack the first time after a lot of sediment has fallen, if you see a lot more fall rack again, it should clear before you rack 3 times but the timing depends on how the mead is clearing and not on a 30-60 day schedule. Best topper is a similar wine, next we like to dilute Everclear with water down to your target alcohol level, even adding some acid blend if you used it in your wine, this doesnt dilute your alcohol and acid levels like just adding water does. If you top off with honey its just going to ferment if its cloudy. A little Welches niagra makes a nice topper while your wine is still fermenting but if its started to clear you dont want to keep adding sugar or it might keep the yeast in suspension and prevent it from clearing sooner. WVMJ